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Chapter 6 Reaction gas chromatography of polymers
Chapter 6
Reaction gas chromatography of polymers In recent years, some work has shown that it is possible, in principle, t o analyze polymers by gas chromatography (GC) with the use of carrier gases at high pressures [ l , 21. The prospects for the wide analytical utilization of this method are still uncertain, however, and it is possible that the use of the rapidly developing technique of liquid chromatograpliy for the analysis of polymer systems will remain the simplest and most efficient method of investigation of high-molecular-weight compounds [3-51 . In recent years, the methods of functional group analysis have undergone great changes because of the wide application of GC [6-81. The combined use of chemical and chromatographic methods has opened up a number of new possibilities; among these, of special significance are the following points: (1) increasing the resolution of the methods of functional group analysis, transforming then1 from methods of group identification into methods of identification of individual compounds, permitting the solution of problems that were previously insoluble; (2) increasing the reliability of the method, in particular the possibility of isolating the end product of the reaction froin the side products; (3) reducing the analysis time; and (4) decreasing the amount of substance necessary for carrying out the functional group analysis. The methods of functional group analysis of non-polymeric organic compounds have been thoroughly developed, and the existing methods have been surveyed in some excellent books [6, 9, 101. The application of these methods t o polymers, however, is possible only after preliminary evaluation, because the solubility of polymers is usually lower than that of monomeric coinpounds, which affects the kinetics of their reactions. If a polymer is insoluble, the existing methods can be applied only for determining the surface functional groups. Also, the reactivity of the functional groups in polymers differs froin that in non-polymeric compounds. As polymers are non-volatile under the usual conditions used in GC, this technique is used for analyzing the volatile products of the degradation of high-molecular-weight compounds, rather than the compounds themselves. In functional group analysis, GC is nua ally applied in combination with chemical methods in which either reactions occur with the formation of volatile products, or one of the initial reagents is a volatile compound. Accordingly, one can distinguish several different methods in the functional group analysis of polymers by cheiiiical reactions combined with GC. Firstly, we should mention reaction methods that lead to the formation of volatile reaction products. Thus, the determination of alkoxyl groups [l 1 1 by boiling the test compound in hydriodic acid using the Zeisel and Fanto method [12] leads t o the formation of the corresponding volatile alkyl iodides, whose chromatographic separation has been described [ 131. In polysiloxanes, the determination of alkoxyl groups can also be achieved by the GC analysis of the alcohols formed on alkaline fusion of the polymer [ 141 . Secondly, for analytical purposes one can use reactions of addition of a volatile reagent t o the polymer with GC determination of the content of the residue of this References p. 156
146
REACTION CC OF POLYMERS
reagent in the reaction mixture upon completion of the reaction. Thus, for instance, this principle served as the basis for determining the content of primary and secondary amino groups in polyethyleneimino by using the reaction of cyanoethylation [ 151 . Thirdly, the content of the separate groups in a polymer can be determined after chemical cleavage of the test polymer into separate volatile compounds. For instance, in carrying out an analysis of a copolymer of ethylene oxide and propylene 1,2-oxide [16] , the copolymer was deconiposed with a 45% solution of hydrogen bromide in glacial acetic acid for 3 h at 150°C. The reaction products contained a mixture of 1,2-dibromoethane and 1,2-dibroniopropane, which were extracted with carbon disulphide and analyzed by GC. In many instances, the realization of methods such as the above may require a series of successive chemical transformations. According to Hellman and Wall [ 171 , chemical methods are often more accurate than physical methods for the investigation of polymers. Certain limitations of chemical methods should also be mentioned [ 161 . With an increase in the molecular weight of the test polymer, the accuracy of determination of the terminal functional groups decreases. Trace impurities may result in qualitative and quantitative errors. Therefore, chemical methods of analysis of terminal groups are mainly applicable to polymers with a molecular weight from 20,000 to 30,000. Also, the reactivity of the functional groups in the polymer changes as a result of the reaction, with a change in the nature of neighbouring groups. Note that reactions in polymers often do not proceed to completion. Fourthly, the determination of the functional g r o u p present in a polymer in small amounts has a number of specific features [ 171 . The general scheme for the investigation of polymeric compounds by reaction GC can be represented as follows. The non-volatile compound to be analyzed, subjected to the action of chemical reagents (acid, alkali, oxygen, etc.) and also physical effects (high temperature, various types of radiation), yields volatile products the nature and amount of which are closely related to the structure and composition of the system being analyzed. Therefore, GC data on the composition of the volatile products of polytner degradation make it possible to characterize more or less fully the composition and structure of the initial polymer. This chapter considers chemical reaction-functional group GC based on specific reactions of chemical reagents with the polymer (which usually proceed with definite functional groups of the polymer), and GC of the volatile products of radiative and photochemical degradation. Pyrolysis GC, which is based on the thermal decomposition of the polymer, is of interest in its own right and is therefore covered in a separate chapter (see Chapter 7). As the determination of functional groups is simplified when the reaction product is a gas we gve opposite a table tor the gasometric determination of organic functional groups (Table 6.1) [9]. The work of Franc and Mike3 [18] provides a brilliant example of the use of splitting reactions, resulting in the formation of gaseous products, with the aim of identifying various nitrogen-containing functional groups. Let us consider the application of reaction GC to the analysis of polyesters. The methods for analyzing linear and branched polyesters and alkyd resins include complete decomposition of the polymer into the initial components by saponification, aminolysis or alcoholysis, conversion of the polar monomeric compounds obtained into derivatives,
REACTION GC OF POLYMERS
147
TABLE 6.1 GASOMbTRIC DETERMINATION OF ORGANIC rUNCTIONAL GRO'LJPS ~
Functional group
Principle of determination
Compound analyzed
Azo Alkene
Iieating with phenylhydrazine Catalytic hydrogenation and determination of absorbed hydrogen Reduction Formation of alkyl iodide, oxidation and reaction of iodic acid with hydrazine Reaction with Grignard reagent Nitrosation Oxidation
Nitrogen Hydrogen
Alkyl nitrate Alkoxyl Aniide and imide Ainine Hydrazine and hydrazide Hydroxyl Diazo Carboxyl Carbonyl
N-Nitro N-Nitroso Semicarbazide Ester
Sulpharnide Quinone Phenol
Reaction with lithium aluminium hydride Heating in the presence of catalyst Decarboxylation with Grignard reagent Reaction with Grignard reagent and decomposition of excess of reagent Reduction with sodium borohydride and determination of excess of reagent Reaction with sulphuric acid and mercury Reduction Reaction with sulphuric acid and mercury Oxidation Reaction with Grignard reagent and decomposition of excess of reagent Reduction with lithium aluminium hydride and decomposition of excess of reagent Oxidation with nitric acid Reaction with phenylhydrazine Reaction with lithium aluminium hydride Reaction with Grignard reagent
Nitrogen oxides Nitrogen Methane Nitrogen Nitrogen Hydrogen Nitrogen Carbon monoxide Methane Methane Hydrogen Nitrogen oxides Nitrogen Nitric oxide Nitrogen Methane Hydrogen Nitrogen dioxide Nitrogen Hydrogen Methane
which are more suitable for GC analysis, and GC analysis proper of the products obtained. Thus, in practice, carboxylic acids are analyzed in the form of the corresponding esters and polyols in the form of the corresponding acetates. As an example, we shall consider the analysis of alkyd resins based on phthalic anhydride and various polyols [ 191 . The resin sample was placed in a flask (1 25 ml), 6 nil of butylaniine was added and the mixture was boiled with an inverted cooler for 1 h. On cooling, 25 nil of acetic anhydride were added and the mixture was boiled for 90 min. Upon cooling, 35 ml of water were added t o the reaction mixture containing acetates of polyhydroxy alcohols and the mixture was boiled for 5-10 min, then cooled, transferred into a separating funnel and extracted with chloroform. The combined extract was washed with water until the acidic reaction disappeared, then filtered through filter-paper moistened with chloroform and collected into a flask (250 nil). Most of the solvent was evaporated in a jet of air over a water-bath, the remainder (5-10 ml) being used for chromatographic analysis. The polyol acetates obtained were determined by References p. 156
REACTION GC OF POLYMERS
148
gas chromatography with a programmed temperature increase from 50 to 225°C at 7.9'C/min on a column (122 X 0.6 cm) filled with 10% Carbowax 20M on Chromosorb W (60-80 mesh). Fig. 6 . l a shows a chromatogram of a mixture of all of the polyols studied on Carbowax 20M. The reaction products of excess of butylamine and acetic anhydride emerge from the column between 14 and 16 min in the form of two small separated peaks. Fig. 6.lb shows a chromatogram of the conversion products of one of the samples of an alkyd resin. Each of the alkyd resins analyzed, based on phthalic anhydride, forms a derivative of o-phthalic acid as reaction product. This product, however, does not interfere in the determination of alcohols. Other isomers of phthalic acid were not separated under these conditions. The method enables one to determine alcohols contained in the mixture at concentrations as low as 1%, but the sensitivity of the determination decreases with increasing boiling temperature. Esposito [20] extended the range of alcohols determined and neopentyl glycol, 1,4butanediol, dipropylene glycol and triethylene glycol were analyzed. Benzylamine was used for aminolysis because n-butylamine masks the peaks of the substances being analyzed. Later, polyvinylformylpropionitrile was proposed as a stationary phase for the separation of polyols [21] as it is stable for a long period at 275°C. Wittendorfer [22] described the application of this method to the analysis of alkyd resins based on trimethylolpropane. The above methods make it possible to determine any polyol contained in an alkyd resin whose acetate can be analyzed by GC. The identification and quantitative analysis of carboxylic acids (components of alkyd and polyester resins) are carried out by GC of the methyl esters. The methyl esters are less polar than the parent acids and are more suitable for GC determination. The
L
1.-
1-1
I
L
L , - -U
Fig. 6.1. (a) Chromatogram of polyol acetates on Carbowax 20M. Peaks: 1 = propylene glycol acetate; 2 = ethylene glycol acetate; 3 = reaction products; 4 = diethylene glycol acetate; 5 = glycerol acetate; 6 = trimethylol acetate; 7 = trimethylolpropane acetate; 8 = pentaerythritol acetate; 9 = mannitol acetate; 10 = sorbitol acetate. (b) Chromatogram of conversion products of an alkyd resin. Peaks: 1 = chloroform; 2 = propylene glycol acetate; 3 = reaction products; 4 = glycerol acetate; 5 = o-phthalic acid.
REACTION GC OF POLYMERS
149
rapid methods developed for the esterification of polymer saponification products ensure the rapid preparation of samples for analysis. The procedure for the preparation of samples [23] for analysis is fairly simple. A resin solution containing about 0.3 g of non-volatile substance was placed in a flask (125 ml), then 15 nil of 0.5 Nlithium methoxide were added; the mixture was heated with an inverted cooler on a water-bath to complete dissolution, and then boiled for a further 2 min. A 5-ml volume of 6 N sulphuric acid was added to the mixture, which was then transferred into a separating funnel. Subsequently, 50 ml of water and 35 ml of methylene chloride were added. The methylene chloride layer was separated, washed with water to a neutral reaction, evaporated to dryness and the residue analyzed by GC. The chromatographic analysis of methyl esters of carboxylic acids was carried out independently with the use of two columns: the first contained silicone grease on Chromosorb W (60-80 mesh), and the second a polar phase (one half was filled with 20% Carbowax 20M on Chromosorb W and the other half with 20% diethylene glycol succinate on Chromosorb W). The separation was carried out with a programmed temperature increase from 75 to 250°C for the column containing the silicone grease and from 125 to 225°C for that containing Carbowax 20M, each at the rate of 4"C/min. The method can be used for investigating resins based on various dicarboxylic acids. It is also possible to determine monocarboxylic acids, which are often present in alkyd and polyester resins. Esposito and Swann 1231 investigated o-phthalic, isophthalic, fumaric, maleic, itaconic, succinic, adipic, azelaic, sehacic, diglycolic, pelargonic and benzoic acids and also lauric, myristic, palmitic, stearic, oleic, linoleic and linolenic acids. Fig. 6.2 illustrates the separation of the methyl esters of some carboxylic acids on columns containing Carbowax 20M and silicone grease. On a polar column containing Carbowax 20M, a more distinct separation is achieved, but isophthalic and o-phthalic acids are eluted as a single peak, while maleic, fumaric, lauric and adipic acids are separated incompletely. On the column containing silicone grease, isophthalic and o-phthalic acids are separated, but some other compounds are eluted from the column as a single peak. The above procedure was used successfully in the analysis of alkyd and polyester resins. The presence of modifying additives such as phenol, rosin, nitrocellulose and melamine- and urea-formaldehyde resins does not affect the results. Tetrachlorophthalic and chlorendic acids cannot be determined by this method, but they do not affect the identification of the other acids. A slightly different version of the determination of the acids contained in alkyd resins was suggested by Gerasimora et al. [24]. A sample of alkyd resin (0.05-0.10 g) is placed in a flask with an inverted cooler, then a 100%excess of a 1%solution of sodium in absolute methanol is added and the mixture is heated for 1 h on a water-bath. A saturated solution of sodium chloride is added and the methyl esters of the acids are extracted with diethyl ether and analyzed by GC at 182°C or 240°C on columns (3 m X 4 mm; 2 m X 4 mm) filled with 20% poly(ethy1ene glycol adipate) on Chromosorb W or 20% Apiezon L on Chromosorb W. Haken [25] proposed a GC method for the analysis of benzoic acid and its p-tert.butyl homologue in the form of the corresponding methyl esters. These compounds are used as chain-length regulators in modified alkyd and linear resins. According to the proposed method [25] , a resin solution is saponified with an alcoholic solution of an References p. 156
REACTION GC OF POLYMERS
150
% 0
a
m L c L
0
c
lJ
aJ
c
c n I
0
10
20
30
0
10
20
30
,
40
Fig. 6.2. Chromatograms of methyl esters of carboxylic acids on columns containing Carbowax 20M (a) and silicone grease (b). (a) Peaks of methyl esters of acids: 1 = pelargonic; 2 = succinic; 3 = benzoic; 4 = maleic or fumaric; 5 = lauric; 6 = adipic; 7 = itaconic; 8 = diglycolic; 9 = myristic; 10 = triacetic; 11 = azelaic; 12 = palmitic; 1 3 = sebacic; 14 = o- or iso-phthalic; 15 = stearic; 16 = oleic; 17 = linoleic; 18 = linolenic. (b) Peaks of methyl esters of acids: 1 = succinic; 2 = benzoic; 3 = diglycolic, maleic and fumaric; 4 = pelargonic, itaconic and adipic; 5 = triacetic; 6 = o-phthalic; 7 = isophthalic; 8 = lauric and azelaic; 9 = sebacic; 10 = myristic; 11 = palmitic; 12 = oleic, linoleic and linolenic; 13 = stearic.
alkali, then the potassium salts of the benzoic and fatty acids are esterified with diazomethane. The separated methyl esters of the acids were analyzed on a column containing 10%butanediol succinate on Celite (80- 100 mesh); the column temperature was increased from 130 to 200°C at 5"C/min. The GC separation of methyl esters of fatty acids has also been described by other workers [26-291. Jankowski and Garner [30] proposed a method for converting esters of fatty acids into their methyl derivatives by re-esterification. The procedure for the re-esterification of esters of carboxylic acids present in plastisizers and polymers was as follows. A sample (0.2-0.5 g) was placed in a flask (250 ml) containing iodine, then 25 ml of 1 N acetic acid, 25 ml of a saturated aqueous solution of sodium chloride and 10 ml of a standard solution of diphenyl ether (internal standard) in benzene were added. The mixture was transferred into a separating funnel and the benzene layer was collected, evaporated to 10 ml and analyzed on the chromatograph. The chromatographic analysis was carried out at 195OC on a column (250 X 0.6 cm) filled with 5% Bentone-34 and 15% Carbowax 20M on Chromosorb 8' (60-80 mesh). Table 6.2 [30] compares the results obtained for some polymeric and monomeric substances when using the methods of re-esterification and saponification. It can be seen that the results are in good agreement, but the former method is preferable because of its simplicity, specificity and rapidity. Free adipic, palmitic and terephthalic acids do not form methyl esters by the above-described method. Monomeric and dimeric acids in alkyds were determined after hydrolysis by converting them into methyl esters (Paylor et al. [31] used a methanolic solution of boron trifluoride). By using a short column (30.5 X 0.3 cm) packed with 5% Dow Corning Hi-Vac silicone grease on Chromosorb W (60-80 mesh), with programmed temperature increase from 170 to 330°C at 15"C/min, and then heating for 5 min at 330°C it was possible to elute all of the monomeric acids in a single peak and the dimeric in another single peak.
REACTION GC OF POLYMERS
151
TABLE 6.2 COMPARISON OF TWO METHODS 1;ORTHE ANALY SIS OF MONOESTERSAND POLYESTERS [ 30) Initial (test) compound
Poly(et1iylene terephthalate) (commercial fibre) Polyester fibre Dietliylene glycol adipate Diphenyl phthalate Dibutyl terephthalate Dibutyl sebacate Dibenzyl succinate Dibenzyl phthalate Sorbitol monolaurate
~
Acid whose methyl ester is determined
Content of acid (%)
Terephthalic
81.0
82.0
Isophthalic Terephthalic Adipic Adipic Phtlialic Terephthalic Sebacic Succinic Phthalic Myristic Lauric Capric Caprylic
10.0 59.1 40.5 66.6 52.2 58.0 60.6 35.5 48.0 11.7 30.1 3.4 3.0
10.0 60.0 41.0 61.6 52.2 58.4 62.9 38.2 47.8 11.5 31.9 3.3 2.8
~
.
~
Re-esterification Saponification
.
Other investigations [32] showed that the analysis of a large number of mono- and dibasic acids is more efficient if n-propyl esters are chroniatographed instead of methyl esters. In this method, the esters were obtained by interaction with n-propanol and boron trifluoride, and separation was carried out on a column packed with 3% poly(ethylene glycol) or 3% silicone oil on Celite. The method for the industrial analysis for unsaturated polyesters is different from the preceding methods in that dibasic acids (methyl esters) and glycols are separated on a single column. The resin is first separated from the solvent (styrene) by re-precipitation from light petroleum [33] and the solid resin is re-esterified with sodium methoxide in methanol for 18 h. The resulting solution of glycols and methyl esters is analyzed directly by GC on a column (336 X 0.6 cm) packed with 20% GE silicone SF-96 on Fluoropak 80 at 1 10, 150 and 18OoC or with a programmed temperature increase from 110 to 180°C at 8"lmin. The GC of polyesters used in the production of polyurethanes has been developed [34]. The method permits the identification of polyesters in a mixture and the determination of the content of oxyethylene and oxypropylene groups. Polyesters are treated with a mixture of acetic anhydride and p-toluenesulphonic acid and the acetylation products are determined by GC. The results obtained by GC and nuclear magnetic resonance spectrometry are in good agreement. A method for the quantitative determination of hydroxyl groups in polymers has been proposed [ 3 5 ] ,based on the interaction of these groups with methylmagnesium iodide and subsequent quantitative determination of the methane released. In order t o separate the methane from the benzene or diethyl ether, which are used as solvents, a column (0.51nX 4 mm) packed with 10%N-methylpyrrolidone on alumina at 351°C was used, while for separating the nitrogen and methane a column (1 .O in X 6 mm) packed with molecular sieve 5 A was used. References p. 156
152
REACTION CC OF POLYMERS
The applications of reaction GC also include the analysis of mononuclear hydroxymethylphenols in the form of acetates in uncured resols [36] . The resol analysis was described in detail by Higginbottom et al. [37]. First, water was removed from the resol, then the hydroxyl groups of the polymer were converted quantitatively into acetates with the aid of acetic anhydride in the presence of pyridine. Removal of water was accompanied by partial loss of free phenol and formaldehyde, but. it completely prevented polymerization. Formaldehyde was present in the dehydrated resol in the form of a polyforrnal, HO * C6H4 CH2 * (OCH2), * OH, which, on acetylation, was stabilized in the form of an acetate, HO C 6 h CH2 (OCH2), OCOCH3, and produced several peaks on the chromatogram. Therefore, formaldehyde was removed in the form of a compound with pyridine bisulphide. The separation of hydroxymethylphenol acetates was carried out on a column (760 X 0.3 cig) filled with silicone SE-30 with a programmed temperature increase from 100 to 300°C at 5-6"C/min. The compounds formed were eluted from the column in the order of increasing molecular weight or, with polymers, of increasing boiling temperature. Benzyl acetate was used as internal standard. In determining 2,4,6-trihydroxymethylplienoltriacetate, it is better to use bis(4-acetoxy-3,5-dimethylplienyl)methaneas internal standard. Phenol derivatives can be chromatographed in the form of trimethylsilyl ethers on a column filled with DC-550 or di-n-butyl tetrachlorophthalate [38], and also in the form of trifluoroacetates [39] on a column filled with silicon oil plus tri-o-phenyl phenylphosphate (3: 1). An ingenious method for determining alkoxy groups in phenol esters by the hydrogenation method has been developed by Klesment and Kasberg [40]. The reaction chromatography of polymers, in which low-molecular-weight products are first formed by the action of the appropriate reagents and are then analyzed by GC, is an efficient method for investigating high-molecular-weight compounds with reactive bonds in the main polymer chain. As an example, we shall describe several chromatographic procedures in which hydrolysis is used in the analysis of the composition of various polymers. In the synthesis of linear polyesters, such as poly(ethy1ene terephthalate), a number of side reactions take place, for instance conversion of ethylene glycol to diethylene glycol. The inclusion of diethylene glycol in the polymer chain has an adverse effect on the properties of the polymer. In the GC determination of the amount of diethylene glycol in poly(ethy1ene terephthalate), the best results were obtained with the use of an inert column (200 X 0.6 cm) filled with 5% Carbowax 20M (30-60 mesh) on Haloport F at 170°C [41]. In this procedure, the polyester sample was saponified with sodium hydroxide for 30 min. These conditions did not ensure complete saponification, but as the saponification kinetics of ethylene glycol and diethylene glycol ether groups are almost identical, the proportions of the contents of the two glycols in the product and hence the ratio of the peaks of the substances analyzed are constant. Upon completion of the saponification reaction, the mixture was acidified with phthalic acid and methanol was added. The concentration of diethylene glycol was then determined from a previwsly plotted calibration graph. Later, a method was woiked out in which a metal column was used [42].The polymer was hydrolyzed under pressure f w 4 h at 230"C, then hydrolyzate was analyzed directly
-
- -
6
REACTION GC OF POLYMERS
153
with the use of benzyl alcohol as internal standard on a column (300 X 0.3 cm) filled with 10%Carbowax 20M on a diatomite support at 180°C. Despite the fact that during hydrolysis at 240°C the polymer decomposes to some extent, Janssen et al. [43] hydrolyzed the polymer sample at 250°C for 16 h, then tetraethylene glycol dimethyl ester (internal standard) was introduced and the mixture was separated on Carbowax a t 290°C. A simpler version for determining diethylene glycol in poly(ethy1ene terephthalate) involving decomposition of the sample with 85% hydrazine at 115"C, has been described [44], The analysis of polyamides by GC [45] was carried out by hydrolyzing the test samples in 6 N hydrochloric acid at 130°C for 24-48 h. The results showed the presence of dicarboxylic acids, hydrochlorides of w-amino acids and diamines in the hydrolyzate. In order to carry out the GC analysis, the active hydrogen atom in the amine and carboxyl groups was repIaced with a trimethylsilyl group by treatment with N,O-bis(trimethylsilylacetamide), thus making it possible to identify the compounds of the above three classes on a single column. The reaction of the dry hydrolysis products with the reagent was carried out under the dry nitrogen in a sealed tube for 2 h at 80°C. The dicarboxylic acids were also analyzed in the form of their methyl esters, for which purpose the hydrolyzate was treated with methanol plus p-toluenesulphonic acid. The high-volatility amines were analyzed in the free state; in order to do this, their hydrochlorides were treated with potassium hydroxide in methanol. The method for determining the composition of copolyamides [46] also includes depolynierization by hydrolysis. A polymer sample was hydrolyzed in 6 N hydrochloric acid. One portion of the hydrolyzate, containing amine hydrochlorides and free acids, was evaporated, esterified with a niethanolic solution of boron trifluoride and extracted with diethyl ether. The ether extract of the methyl esters was chromatographed on a column (200 X 0.6 cm) filled with 5% diethylene glycol adipate on Chromosorb W treated with an acid (60-80 mesh). Azelaic acid, which was used as the internal standard, was added prior to esterification. A second portion of the hydrolyzate was neutralized with sodium hydroxide in order to isolate the amines and convert dibasic acids into sodium salts. The free amines were extracted with n-butanol and chromatographed on a column filled with 10%Apeizon L deposited on glass beads. Both columns were heated with a programmed temperature increase from 100 to 220°C at S"C/min. The relative error of the determination was k 5%. The quantitative and qualitative determination of alkoxyl groups in acrylic copolymers can be achieved by taking advantage of the cleavage of the alkoxyl groups by a mixture of potassium iodide and orthophosphoric acid upon heating for 2 h to 200°C [47] . The alkyl iodides released are absorbed by n-hexane on cooling the trap to -75°C; they then are analyzed by GC. For polyacrylates, a method was devised in which the alcohols formed as a result of saponification of the polymer were analyzed on a colurnn (122 X 0.6 cni) filled with 23% Oronit NI-W on firebrick (42-60 mesh) [48] . The polymer sample was dissolved in tetrahydrofuran and saponified with an alcoholic solution of potassium hydroxide at 160°C for 4 h, then the contents were neutralized and chromatographed. This method was used to analyze decyl, lauryl and 2-ethylhexyl acrylates.
References p. 156
154
REACTION G C OF POLYMERS
Earlier work [49] dealt with hydrolysis of copolymers of trioxan and the glycolformyl of orthophosphoric acid with subsequent separation of the products on dodecyl phthalate or a silicone stationary phase at 150°C. Interaction with orthophosphoric acid was also used for determining the weight ratio of oxypropylene and oxyethylene groups in poly(propy1ene oxide) and poly(ethy1ene oxide) [ S O ] . The polymer sample reacted with the orthophosphoric acid in an inert atmosphere at 350°C at the chromatograph inlet, forming propionaldehyde and acetyldehyde, respectively. The percentage of oxyalkylene groups was proportional to the amount of the aldehyde formed. Hydrolysis and GC have been used for analyzing copolymers of cis- and trans-cyclohexanediol-1,2 [51 1 , diisopropyl esters of polyoxymethylene [52] ,cyano-containing polymers [53] and also other polyesters [54] and alkyd resins [55]. It should be noted that in many instances the method permits the determination not only of the initial monomeric compounds, but also of the distribution of the monomers in the copolymer. Thus, for instance, hydrolysis and combined GC nuclear magnetic resonance analysis have been used for determining the distribution of isomers in propylene oxide-maleic anhydride block copolymers [56] and propylene oxidecitraconic anhydride block copolymers [56, 571 prepared on different catalysts. Glycol esters were separated on a column filled with mercury(I1) chloride and Carbowax 20M on Chromosorb CL (60-80 mesh). A similar method was used for establishing the distribution of monomers in polysulphite esters obtained by copolymerization of propylene oxide and sulphur dioxide on different catalysts [58]. In analytical practice, use is also made of polymer cleavage (as a result of a reaction with hydrogen bromide) with subsequent analysis of the bromide formed. For determining the composition of copolymers of methyl methacrylate, ethyl acrylate and butyl maleinate [59, 601, the combined uses of Zeisel’s method and GC has been suggested. At first [59], the method was intended for determining the composition of copolymers of methyl methacrylate with ethyl acrylate that contained less than 10%of the latter. The alkoxyl groups of the copolymer were converted into the corresponding alkyl iodides with the aid of hydriodic acid in a phenol solution, then the iodides were isolated and chromatographed on a column containing dinonyl phthalate on Celite at 150°C. Methylene chloride and ethylene chloride were used as internal standards for methyl and ethyl iodides, respectively. Later [60], in order to determine butyl maleate, which is also present in the copolymer, the analysis was carried out on a column (300 X 0.6 cni) filled with di-2-ethylhexylsebacate on firebrick at 70°C. This method was also used successfully for analyzing the weight ratio of oxyethylene and oxypropylene groups in alkylene oxide polymers [61, 621 . A polymer sample (20 mg) was converted into the dibromide by interaction with excess of a 45-50% mixture of acetic and hydrobroniic acids at 150°C for 2 h [61]. The bromides formed were dissolved in carbon disulphide and analyzed on a glass column (90 X 0.4 cm) filled with 30% silicone E-301 on Celite (30-60 mesh) at 65°C. Using the ozonation reactiw with subsequent GC analysis of aldehydes and acids, one can determine the micro-structure of rubbers [63] .
REACTION GC OF POLYMERS
155
On interaction with BF30(C2H5)2,methylsiloxane form fluorosilanes, the GC analysis of wluch yields the ratios of the groups (CH3)3Si, (CH3)*Si and CH3Si in the polymers [64] . The disadvantage of this method is that the time required t o complete the reaction at 70°C is 96 h. The fluorosilanes formed were cooled with a mixture of dry-ice and acetone, then dissolved in diethyl ether and analyzed on a capillary column (4600 X 0.05 cm) filled with silicone SE-30, and a column (122 X 0.6 cm) filled with 16.6%squalane on Teflon-6 at 35°C. In this reaction, the ethylsiloxane groups are converted into C2H5SiF5, which is eluted simultaneously with (CH&SiF*. Therefore, in practice the method is restricted t o the investigation of methylsiloxane polymers. Vinyl groups of silicone rubbers, after interaction with orthophosphoric acid (in order t o convert the vinyl groups into ethylene) [65] , are also determined chromatographically on a column (1 12 X 0.6 cm) filled with alumina a t 65°C. A modification of this method was described by Krasikova and co-workers [66,67]. The structural analysis of polysiloxanes by GC and thermal analysis was developed by Franc et al. [68]. Note that in trying t o establish the structure of a polymer, it is also advisable t o use data on its elemental composition. Methods of elemental analysis involving the use of GC have been described [8, 69, 701. The reaction on polyniers t o physical factors such as radiolysis and ultraviolet (W) light, coupled with subsequent GC analysis of the volatile decomposition products, is an additional means for characterizing polymers. The radiation-chemical method can be used for the quantitative identification of polymers. Berezkin et al. [71] studied the dependence of the range of gaseous radiolysis products on the polymer structure in the series polyethylene, polypropylene, polyisobutylene, which differ, among other things, in the concentrations and positions of the methyl groups. A weighed polymer sample was placed in a glass ampoule, which was evacuated t o mni, sealed and irradiated with y-rays (from a cobalt-60 source) at a dose rate of 1.7 1OI6 eV/g sec. The gaseous radiolysis products were analyzed chronlatographically. The method has a high sensitivity t o hydrocarbon substituents in the main chain. The sensitivity t o lateral branchings in the main chain permits, in particular, low- and high-pressure polyethylenes t o be distinguished. The effect of radiation on copolymers of vinyl acetate with ethylene makes it possible t o determine the quantitative composition of the copolymer. When a polymer sample is subjected t o 100 Mrad of y-radiation (721 , low-molecular-weight hydrocarbons, carbon monoxide, carbon dioxide and hydrogen are formed. The amount of carbon monoxide not detected in the decomposition products of pure polyethylene is proportional t o the vinyl acetate content in the copolymer. The accuracy of the determination is 1%. In investigations on the degradation of polymers under the effect of electrons [73], it was shown that in branched polyethylene, ethyl and butyl radicals are located after each 100 carbon atoms. On irradiation of polypropylene, methane is formed, which indicates the absence of recombination of the methyl radicals under the conditions used. Low-volatility compounds can be analyzed by the photodecomposition method [74, 751 A mercury-saturated sample was placed in a silica capillary tube, which was evacuated and sealed. The sample was then irradiated from a mercury source. The chroinatograms obtained after irradiation are simple and reproducible. The method can be used
-
*
References p. 156
156
REACTION GC OF POLYMERS
successfully in standard determinations, and also for estimating the photodecomposition stability of the polymer. The combination of photodecomposition with GC is used for estimating UV adsorption in polymers [76]. Samples of polymer film in a silica vessel were irradiated from a standard UV lamp, then the degree of decomposition of the film was estimated by analyzing, at definite time intervals, the gaseous decomposition products. A column (200 X 0.635 cm) filled with poly(propy1ene glycol) on Chromosorb W at 100°C was used. The chromatograms of films of acrylonitrocellulose containing 54-55% of poly(methy1 methacrylate), 24-26% of dinitrocellulose, 19-2 1% of dioctyl phthalate and 1% of absorber have seven main peaks, varying in height. The decomposition of the polymer is proportional to the efficiency of the absorber. Of the several absorbers investigated, 2,2'-dihydroxy-4-methoxybenzophenone (Cyasorb UV-24) was the most efficient. Thus, the investigation and analysis of polymers by reaction GC make it possible to determine a number of important characteristics of high-molecular-weight compounds: the proportions of the initial monomeric compounds, the distribution of monomers in the polymer chain, the content of the separate functional groups, etc. Unfortunately, the development of these methods has not been given sufficient attention until recently. The level of application of reaction GC methods in polymer analysis is considerably lower than their apparent potential. In our opinion, one of the factors restricting the application of chromatographic methods is the lack of systematic manuals on the use of gas chromatography in the functional group analysis of organic compounds, including polymers.
REFERENCES 1 L. McLaren, M. N. Myers and J. C. Giddings, Science, 159 (1968) 197. 2 G. W. Rijnder, J. P. A. Bleumer and M. van Krevelen, in K. V. Chutov and K. 1. Sakodynsky (Editors), Uspekhi Khromatografii (Advances in Chromatography), Nauka, Moscow, 1972, p. 65. 3 Z. Deyl, K. Macek and J. Jan& (Editors), Liquid Column Chromatography - A Survey ofModern Techniques and Applications, (Journal of Chromatography Library, Vol. 3), Elsevier, Amsterdam, 1975. 4 J. J. Kirkland (Editor), Modern Practice o f Liquid Chromatography, Wiley-Ipterscience, New York, London, Sydney, Toronto, 1971. 5 S. G. Perry, R. Amos and P. 1. Brewer, Practical Liquid Chromatography, Plenum Press, New York, London, 1972. 6 S. Siggia (Editor), Instrumental Methods of Organic Functional Group Analysis, Wiley-Interscience, New York, London, Sydney, Toronto, 1972. 7 V. G. Berezkin, V. S. Tatarinsky, M. V. Palyanova and M. M. Fedyachkin, Usp. Khim., 4 3 (1974) 2088. 8 V. G. Berezkin, Analytical Reaction Gas Chromatography, Plenum Press, New York, 1968. 9 N. D. Cheronis and T. S. Ma, Organic Functional Group Analysis by Micro and Semimicro Methods, Interscience, New York, London, Sydney, 1964. 10 L. S. Ettre and W. H. McFadden (Editors), Ancillary Techniques of Gas Chromatography, WileyInterscience, New York, London, Sydney, Toronto, 1969. 11 L. V. Kolesnik and M. N. Chuniachenko, Izv. Akad. Nauk SSSR, Ser, Khim, (1969) 2107. 12 S. Zeisel and R. Fanto, Z. Anal. Chetn, 4 2 (1903) 549. 13 G. Castello, G. D'Amato and E. Biagini,L Chromatogr., 41 (1969) 313.
REFERENCES
157
14 C. L. Hanson and R. C. Smith,Anal. Chem., 44 (1972) 1571. 15 V. G. Berezkin, G. L. Groniova and T. P. Golitsyna, Vysokomol Soedin.. Ser. A, 17 (1975) 1177. 16 J. B. Stead and A. H. Hindley, J. Chromatogr., 42 (1969) 470. 17 M. Hellman and L. A. Wall, in G. M. Kline (Editor), Analytical Chemistry ofPolynzers, Part III, Identification Procedures and Chemical Analysis, Interscience, New York, London, 1963. 18 J. Franc and F. Mikes, J. Chromatogr., 26 (1967) 378. 19 G. G. Esposito and M. H. Swann, Anal. Chem., 33 (1961) 1854. 20 G. G. Esposito, Anal. Chem., 34 (1962) 1173. 21 K. Assmann, 0. Serfas and G . Geppert, J. Chromatogr., 26 (1967) 495. 22 R. E. Wittendorfer, Anal. Chem., 36 (1964) 930. 23 G. G. Esposito and M. H. Swann, Anal. Chem., 34 (1962) 1048. 24 L. 1. Gerasiniova, V. R. Zlobina and G. A. Ermolayeva, Lakokrasoch. Muter. Ikh. Primen., No. 2 (1970) 58. 25 J. K. Haken, J. Gas Chromatogr., 2 (1964) 263. 26 S. Dal Nogare and R. S . Juvet, Anal. Chem., 34 (1962) 35P. 27 C. W. Gehske and D. F. Goerlitz, Anal. Chem., 35 (1963) 76. 28 1. Hornstein and P. F. Growe, Anal. Chem., 33 (1961) 310. 29 0. Mlejnek, Chern. Prfim, 14 (1964) 586. 30 S. Jankowski and P. Garner, Anal. Chem., 37 (1965) 1709. 31 R. A. L. Paylor, R. Feinland and N. H. Conroy, Anal Chem., 40 (1968) 1358. 32 A. J. Appleby and J. E. Mayne, J. Gas Chromatogr., 5 (1967) 266. 33 D. F. Percival, Anal. Chem., 35 (1963) 236. 34 K. Tsuji and K. Konishi, Analyst (London), 99 (1974) 54. 35 K. V. Alekseyeva and L. P. Khramova, Zh. Anal Khim., 27 (1972) 163. 36 S. H. Rider and E. E. Hardy, Advan. Chem., 34 (1972) 173. 37 H. P. Higginbottom, H. M. Culbertson and J. S. Woodbrey, Anal. Chem., 37 (1965) 1021. 38 S. H. Lander, P. Pantages and F. Wender, Chem. Ind. (London), (1958) 1664. 39 A. T. Shulgin, Anal. Chem., 36 (1964) 920. 40 I. Klesment and A. Kasberg, Microchim. Acta, (1967) 1136. 41 D. R. Gaskill, A. G. Chasar and C. A. Luchesi, Anal. Chem., 39 (1967) 106. 42 L. H. Polder, Anal Chem., 40 (1968) 228. 43 R. Janssen, H. Ruysschaert and R. Vroom, Makromol. Chem., 77 (1964) 153. 44 H.-D. Dinse and E. TuEer, Faserforsch. Textiltech., 21 (1970) 205. 45 H. Tengler, Plastverarbeiter, 22 (1971) 329. 46 A. Anton, Anal. Chem., 40 (1968) 11 16. 47 V. R. Zlobina, N. P. Zvyagintseva, L. 1. Gerasiniova and T. A. Ermolayeva, Lakokrasoch. Muter. Ikh. Primen.. No. 6 (1972) 55. 48 J. G. Gobler and E. P. Samsel, SPL Trans., 2 (1962) 145. 49 H. Cherdron, L. Hohr and W. Kern, Angew. Chem., 73 (1961) 215. 50 E. J. Bockowski and H. M. Heresh, 3rd Middle Atlantic Regional Meeting of the American Chemical Society, February, 1968. 5 1 R. Nowicki, Bull. Acad. Pol. Sci. Ser. Sci Chim., 11 (1968) 557. 52 E. Klein, J. Smith and R. J. Eskert, J. Appl. Polym. S c i , 7 (1963) 383. 53 D. G. Val’kovsky, V. N. Robas, S. V. Rogozhin, A. M. Polyakova, V. V. Korshak, K. A. Mager and V. N. Semintsev, Zavod. Lab., 34 (1968) 528. 54 0. Mlejnek, Chem. M m , 1 3 (1963) 105. 55 J. K. Haken,Aust. Paint J., 13 (1967) 11. 56 R. J. Kern and J . Schaefer, J. Amer. Chem. Soc., 89 (1967) 6. 57 J. Schaefer, R. J. Katnik and R. 3. Kern, Macromolecules, 1 (1968) 101. 58 J. Schaefer, R. J . Kern and R. J. Katnik, Macromolecules, 1 (1968) 107. 59 J. Haslain, J. B. Hamilton and A. R. Jeffs,Analyst(London), 83 (1958) 66. 60 D. L. Miller, E. P. Sanisel and J . G. Cobler, Anal. Chem., 33 (1961) 677. 61 A. Mathias and N. Mellor, Anal. Chem.. 38 (1966) 472. 62 M. Filipska, Z. Hippe, T. Krryjanowska and T. Stazeczek, Chem. Anal. (Warsaw), 12 (1967) 39.
158
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63 G. M. Akhmedli and A. N. Perelman, Vysokomol. Soedin., 8 (1966) 61. 64 G. W. Heylmun and J. E. Pikula,J. Gas Chromatogr., 3 (1965) 266. 65 G. W.Heylmun, R. L. Bujarski and H. B. Bradley,J. Gas Chromatogr., 2 (1964) 300. 66 V. M. Krasikova and A. N. Kaganova, Zh. Anal. Khim, 25 (1970) 1409. 67 V. P. Mileshkevitch, V. M. Krasikova, A. H. Kachanova, A. V. Kerlin and T. N. Pratova, Author’s Certificate, No. 395,769, Applied 6.7.71; published 25.1.74. 68 J. Franc, K. PlaEer and F. Mike& Collect. Czech. Chem Commun., 32 (1967) 2242. 69 F. Salzer, Microchem J.,16 (1971) 145. 70 H. Kelker, in H. G. Struppe (Editor), Aspects of Gas Chromatography, Akademie-Verlag, Berlin, 1971, p. 37. 71 V. G. Berezkin, Yu. A. Kalbanovksy and E. A. Kyazimov, Vysokomol. Soedin.,Ser. A , 9 (1967) 2566. 72 R. M. Kamath and A. Barlow, Anal. Chem., 37 (1965) 1266. 73 R. Salovey and J. V. Pascale, J. Polym. Sci, Part A-2, (1964) 2041. 74 R. S. Juvet, 11.and L. P. Turner,Anal. Chew., 37 (1965) 1464. 75 R. S. Juvet, Jr., R. L. Tanner and J. C. Y. Tsao, J. Gas Chromatogr., 5 (1967) 15. 76 H. C. Su and J. L. Cameron, Anal. Chem., 39 (1967) 949.
Reaction gas chromatography of polymers In recent years, some work has shown that it is possible, in principle, t o analyze polymers by gas chromatography (GC) with the use of carrier gases at high pressures [ l , 21. The prospects for the wide analytical utilization of this method are still uncertain, however, and it is possible that the use of the rapidly developing technique of liquid chromatograpliy for the analysis of polymer systems will remain the simplest and most efficient method of investigation of high-molecular-weight compounds [3-51 . In recent years, the methods of functional group analysis have undergone great changes because of the wide application of GC [6-81. The combined use of chemical and chromatographic methods has opened up a number of new possibilities; among these, of special significance are the following points: (1) increasing the resolution of the methods of functional group analysis, transforming then1 from methods of group identification into methods of identification of individual compounds, permitting the solution of problems that were previously insoluble; (2) increasing the reliability of the method, in particular the possibility of isolating the end product of the reaction froin the side products; (3) reducing the analysis time; and (4) decreasing the amount of substance necessary for carrying out the functional group analysis. The methods of functional group analysis of non-polymeric organic compounds have been thoroughly developed, and the existing methods have been surveyed in some excellent books [6, 9, 101. The application of these methods t o polymers, however, is possible only after preliminary evaluation, because the solubility of polymers is usually lower than that of monomeric coinpounds, which affects the kinetics of their reactions. If a polymer is insoluble, the existing methods can be applied only for determining the surface functional groups. Also, the reactivity of the functional groups in polymers differs froin that in non-polymeric compounds. As polymers are non-volatile under the usual conditions used in GC, this technique is used for analyzing the volatile products of the degradation of high-molecular-weight compounds, rather than the compounds themselves. In functional group analysis, GC is nua ally applied in combination with chemical methods in which either reactions occur with the formation of volatile products, or one of the initial reagents is a volatile compound. Accordingly, one can distinguish several different methods in the functional group analysis of polymers by cheiiiical reactions combined with GC. Firstly, we should mention reaction methods that lead to the formation of volatile reaction products. Thus, the determination of alkoxyl groups [l 1 1 by boiling the test compound in hydriodic acid using the Zeisel and Fanto method [12] leads t o the formation of the corresponding volatile alkyl iodides, whose chromatographic separation has been described [ 131. In polysiloxanes, the determination of alkoxyl groups can also be achieved by the GC analysis of the alcohols formed on alkaline fusion of the polymer [ 141 . Secondly, for analytical purposes one can use reactions of addition of a volatile reagent t o the polymer with GC determination of the content of the residue of this References p. 156
146
REACTION CC OF POLYMERS
reagent in the reaction mixture upon completion of the reaction. Thus, for instance, this principle served as the basis for determining the content of primary and secondary amino groups in polyethyleneimino by using the reaction of cyanoethylation [ 151 . Thirdly, the content of the separate groups in a polymer can be determined after chemical cleavage of the test polymer into separate volatile compounds. For instance, in carrying out an analysis of a copolymer of ethylene oxide and propylene 1,2-oxide [16] , the copolymer was deconiposed with a 45% solution of hydrogen bromide in glacial acetic acid for 3 h at 150°C. The reaction products contained a mixture of 1,2-dibromoethane and 1,2-dibroniopropane, which were extracted with carbon disulphide and analyzed by GC. In many instances, the realization of methods such as the above may require a series of successive chemical transformations. According to Hellman and Wall [ 171 , chemical methods are often more accurate than physical methods for the investigation of polymers. Certain limitations of chemical methods should also be mentioned [ 161 . With an increase in the molecular weight of the test polymer, the accuracy of determination of the terminal functional groups decreases. Trace impurities may result in qualitative and quantitative errors. Therefore, chemical methods of analysis of terminal groups are mainly applicable to polymers with a molecular weight from 20,000 to 30,000. Also, the reactivity of the functional groups in the polymer changes as a result of the reaction, with a change in the nature of neighbouring groups. Note that reactions in polymers often do not proceed to completion. Fourthly, the determination of the functional g r o u p present in a polymer in small amounts has a number of specific features [ 171 . The general scheme for the investigation of polymeric compounds by reaction GC can be represented as follows. The non-volatile compound to be analyzed, subjected to the action of chemical reagents (acid, alkali, oxygen, etc.) and also physical effects (high temperature, various types of radiation), yields volatile products the nature and amount of which are closely related to the structure and composition of the system being analyzed. Therefore, GC data on the composition of the volatile products of polytner degradation make it possible to characterize more or less fully the composition and structure of the initial polymer. This chapter considers chemical reaction-functional group GC based on specific reactions of chemical reagents with the polymer (which usually proceed with definite functional groups of the polymer), and GC of the volatile products of radiative and photochemical degradation. Pyrolysis GC, which is based on the thermal decomposition of the polymer, is of interest in its own right and is therefore covered in a separate chapter (see Chapter 7). As the determination of functional groups is simplified when the reaction product is a gas we gve opposite a table tor the gasometric determination of organic functional groups (Table 6.1) [9]. The work of Franc and Mike3 [18] provides a brilliant example of the use of splitting reactions, resulting in the formation of gaseous products, with the aim of identifying various nitrogen-containing functional groups. Let us consider the application of reaction GC to the analysis of polyesters. The methods for analyzing linear and branched polyesters and alkyd resins include complete decomposition of the polymer into the initial components by saponification, aminolysis or alcoholysis, conversion of the polar monomeric compounds obtained into derivatives,
REACTION GC OF POLYMERS
147
TABLE 6.1 GASOMbTRIC DETERMINATION OF ORGANIC rUNCTIONAL GRO'LJPS ~
Functional group
Principle of determination
Compound analyzed
Azo Alkene
Iieating with phenylhydrazine Catalytic hydrogenation and determination of absorbed hydrogen Reduction Formation of alkyl iodide, oxidation and reaction of iodic acid with hydrazine Reaction with Grignard reagent Nitrosation Oxidation
Nitrogen Hydrogen
Alkyl nitrate Alkoxyl Aniide and imide Ainine Hydrazine and hydrazide Hydroxyl Diazo Carboxyl Carbonyl
N-Nitro N-Nitroso Semicarbazide Ester
Sulpharnide Quinone Phenol
Reaction with lithium aluminium hydride Heating in the presence of catalyst Decarboxylation with Grignard reagent Reaction with Grignard reagent and decomposition of excess of reagent Reduction with sodium borohydride and determination of excess of reagent Reaction with sulphuric acid and mercury Reduction Reaction with sulphuric acid and mercury Oxidation Reaction with Grignard reagent and decomposition of excess of reagent Reduction with lithium aluminium hydride and decomposition of excess of reagent Oxidation with nitric acid Reaction with phenylhydrazine Reaction with lithium aluminium hydride Reaction with Grignard reagent
Nitrogen oxides Nitrogen Methane Nitrogen Nitrogen Hydrogen Nitrogen Carbon monoxide Methane Methane Hydrogen Nitrogen oxides Nitrogen Nitric oxide Nitrogen Methane Hydrogen Nitrogen dioxide Nitrogen Hydrogen Methane
which are more suitable for GC analysis, and GC analysis proper of the products obtained. Thus, in practice, carboxylic acids are analyzed in the form of the corresponding esters and polyols in the form of the corresponding acetates. As an example, we shall consider the analysis of alkyd resins based on phthalic anhydride and various polyols [ 191 . The resin sample was placed in a flask (1 25 ml), 6 nil of butylaniine was added and the mixture was boiled with an inverted cooler for 1 h. On cooling, 25 nil of acetic anhydride were added and the mixture was boiled for 90 min. Upon cooling, 35 ml of water were added t o the reaction mixture containing acetates of polyhydroxy alcohols and the mixture was boiled for 5-10 min, then cooled, transferred into a separating funnel and extracted with chloroform. The combined extract was washed with water until the acidic reaction disappeared, then filtered through filter-paper moistened with chloroform and collected into a flask (250 nil). Most of the solvent was evaporated in a jet of air over a water-bath, the remainder (5-10 ml) being used for chromatographic analysis. The polyol acetates obtained were determined by References p. 156
REACTION GC OF POLYMERS
148
gas chromatography with a programmed temperature increase from 50 to 225°C at 7.9'C/min on a column (122 X 0.6 cm) filled with 10% Carbowax 20M on Chromosorb W (60-80 mesh). Fig. 6 . l a shows a chromatogram of a mixture of all of the polyols studied on Carbowax 20M. The reaction products of excess of butylamine and acetic anhydride emerge from the column between 14 and 16 min in the form of two small separated peaks. Fig. 6.lb shows a chromatogram of the conversion products of one of the samples of an alkyd resin. Each of the alkyd resins analyzed, based on phthalic anhydride, forms a derivative of o-phthalic acid as reaction product. This product, however, does not interfere in the determination of alcohols. Other isomers of phthalic acid were not separated under these conditions. The method enables one to determine alcohols contained in the mixture at concentrations as low as 1%, but the sensitivity of the determination decreases with increasing boiling temperature. Esposito [20] extended the range of alcohols determined and neopentyl glycol, 1,4butanediol, dipropylene glycol and triethylene glycol were analyzed. Benzylamine was used for aminolysis because n-butylamine masks the peaks of the substances being analyzed. Later, polyvinylformylpropionitrile was proposed as a stationary phase for the separation of polyols [21] as it is stable for a long period at 275°C. Wittendorfer [22] described the application of this method to the analysis of alkyd resins based on trimethylolpropane. The above methods make it possible to determine any polyol contained in an alkyd resin whose acetate can be analyzed by GC. The identification and quantitative analysis of carboxylic acids (components of alkyd and polyester resins) are carried out by GC of the methyl esters. The methyl esters are less polar than the parent acids and are more suitable for GC determination. The
L
1.-
1-1
I
L
L , - -U
Fig. 6.1. (a) Chromatogram of polyol acetates on Carbowax 20M. Peaks: 1 = propylene glycol acetate; 2 = ethylene glycol acetate; 3 = reaction products; 4 = diethylene glycol acetate; 5 = glycerol acetate; 6 = trimethylol acetate; 7 = trimethylolpropane acetate; 8 = pentaerythritol acetate; 9 = mannitol acetate; 10 = sorbitol acetate. (b) Chromatogram of conversion products of an alkyd resin. Peaks: 1 = chloroform; 2 = propylene glycol acetate; 3 = reaction products; 4 = glycerol acetate; 5 = o-phthalic acid.
REACTION GC OF POLYMERS
149
rapid methods developed for the esterification of polymer saponification products ensure the rapid preparation of samples for analysis. The procedure for the preparation of samples [23] for analysis is fairly simple. A resin solution containing about 0.3 g of non-volatile substance was placed in a flask (125 ml), then 15 nil of 0.5 Nlithium methoxide were added; the mixture was heated with an inverted cooler on a water-bath to complete dissolution, and then boiled for a further 2 min. A 5-ml volume of 6 N sulphuric acid was added to the mixture, which was then transferred into a separating funnel. Subsequently, 50 ml of water and 35 ml of methylene chloride were added. The methylene chloride layer was separated, washed with water to a neutral reaction, evaporated to dryness and the residue analyzed by GC. The chromatographic analysis of methyl esters of carboxylic acids was carried out independently with the use of two columns: the first contained silicone grease on Chromosorb W (60-80 mesh), and the second a polar phase (one half was filled with 20% Carbowax 20M on Chromosorb W and the other half with 20% diethylene glycol succinate on Chromosorb W). The separation was carried out with a programmed temperature increase from 75 to 250°C for the column containing the silicone grease and from 125 to 225°C for that containing Carbowax 20M, each at the rate of 4"C/min. The method can be used for investigating resins based on various dicarboxylic acids. It is also possible to determine monocarboxylic acids, which are often present in alkyd and polyester resins. Esposito and Swann 1231 investigated o-phthalic, isophthalic, fumaric, maleic, itaconic, succinic, adipic, azelaic, sehacic, diglycolic, pelargonic and benzoic acids and also lauric, myristic, palmitic, stearic, oleic, linoleic and linolenic acids. Fig. 6.2 illustrates the separation of the methyl esters of some carboxylic acids on columns containing Carbowax 20M and silicone grease. On a polar column containing Carbowax 20M, a more distinct separation is achieved, but isophthalic and o-phthalic acids are eluted as a single peak, while maleic, fumaric, lauric and adipic acids are separated incompletely. On the column containing silicone grease, isophthalic and o-phthalic acids are separated, but some other compounds are eluted from the column as a single peak. The above procedure was used successfully in the analysis of alkyd and polyester resins. The presence of modifying additives such as phenol, rosin, nitrocellulose and melamine- and urea-formaldehyde resins does not affect the results. Tetrachlorophthalic and chlorendic acids cannot be determined by this method, but they do not affect the identification of the other acids. A slightly different version of the determination of the acids contained in alkyd resins was suggested by Gerasimora et al. [24]. A sample of alkyd resin (0.05-0.10 g) is placed in a flask with an inverted cooler, then a 100%excess of a 1%solution of sodium in absolute methanol is added and the mixture is heated for 1 h on a water-bath. A saturated solution of sodium chloride is added and the methyl esters of the acids are extracted with diethyl ether and analyzed by GC at 182°C or 240°C on columns (3 m X 4 mm; 2 m X 4 mm) filled with 20% poly(ethy1ene glycol adipate) on Chromosorb W or 20% Apiezon L on Chromosorb W. Haken [25] proposed a GC method for the analysis of benzoic acid and its p-tert.butyl homologue in the form of the corresponding methyl esters. These compounds are used as chain-length regulators in modified alkyd and linear resins. According to the proposed method [25] , a resin solution is saponified with an alcoholic solution of an References p. 156
REACTION GC OF POLYMERS
150
% 0
a
m L c L
0
c
lJ
aJ
c
c n I
0
10
20
30
0
10
20
30
,
40
Fig. 6.2. Chromatograms of methyl esters of carboxylic acids on columns containing Carbowax 20M (a) and silicone grease (b). (a) Peaks of methyl esters of acids: 1 = pelargonic; 2 = succinic; 3 = benzoic; 4 = maleic or fumaric; 5 = lauric; 6 = adipic; 7 = itaconic; 8 = diglycolic; 9 = myristic; 10 = triacetic; 11 = azelaic; 12 = palmitic; 1 3 = sebacic; 14 = o- or iso-phthalic; 15 = stearic; 16 = oleic; 17 = linoleic; 18 = linolenic. (b) Peaks of methyl esters of acids: 1 = succinic; 2 = benzoic; 3 = diglycolic, maleic and fumaric; 4 = pelargonic, itaconic and adipic; 5 = triacetic; 6 = o-phthalic; 7 = isophthalic; 8 = lauric and azelaic; 9 = sebacic; 10 = myristic; 11 = palmitic; 12 = oleic, linoleic and linolenic; 13 = stearic.
alkali, then the potassium salts of the benzoic and fatty acids are esterified with diazomethane. The separated methyl esters of the acids were analyzed on a column containing 10%butanediol succinate on Celite (80- 100 mesh); the column temperature was increased from 130 to 200°C at 5"C/min. The GC separation of methyl esters of fatty acids has also been described by other workers [26-291. Jankowski and Garner [30] proposed a method for converting esters of fatty acids into their methyl derivatives by re-esterification. The procedure for the re-esterification of esters of carboxylic acids present in plastisizers and polymers was as follows. A sample (0.2-0.5 g) was placed in a flask (250 ml) containing iodine, then 25 ml of 1 N acetic acid, 25 ml of a saturated aqueous solution of sodium chloride and 10 ml of a standard solution of diphenyl ether (internal standard) in benzene were added. The mixture was transferred into a separating funnel and the benzene layer was collected, evaporated to 10 ml and analyzed on the chromatograph. The chromatographic analysis was carried out at 195OC on a column (250 X 0.6 cm) filled with 5% Bentone-34 and 15% Carbowax 20M on Chromosorb 8' (60-80 mesh). Table 6.2 [30] compares the results obtained for some polymeric and monomeric substances when using the methods of re-esterification and saponification. It can be seen that the results are in good agreement, but the former method is preferable because of its simplicity, specificity and rapidity. Free adipic, palmitic and terephthalic acids do not form methyl esters by the above-described method. Monomeric and dimeric acids in alkyds were determined after hydrolysis by converting them into methyl esters (Paylor et al. [31] used a methanolic solution of boron trifluoride). By using a short column (30.5 X 0.3 cm) packed with 5% Dow Corning Hi-Vac silicone grease on Chromosorb W (60-80 mesh), with programmed temperature increase from 170 to 330°C at 15"C/min, and then heating for 5 min at 330°C it was possible to elute all of the monomeric acids in a single peak and the dimeric in another single peak.
REACTION GC OF POLYMERS
151
TABLE 6.2 COMPARISON OF TWO METHODS 1;ORTHE ANALY SIS OF MONOESTERSAND POLYESTERS [ 30) Initial (test) compound
Poly(et1iylene terephthalate) (commercial fibre) Polyester fibre Dietliylene glycol adipate Diphenyl phthalate Dibutyl terephthalate Dibutyl sebacate Dibenzyl succinate Dibenzyl phthalate Sorbitol monolaurate
~
Acid whose methyl ester is determined
Content of acid (%)
Terephthalic
81.0
82.0
Isophthalic Terephthalic Adipic Adipic Phtlialic Terephthalic Sebacic Succinic Phthalic Myristic Lauric Capric Caprylic
10.0 59.1 40.5 66.6 52.2 58.0 60.6 35.5 48.0 11.7 30.1 3.4 3.0
10.0 60.0 41.0 61.6 52.2 58.4 62.9 38.2 47.8 11.5 31.9 3.3 2.8
~
.
~
Re-esterification Saponification
.
Other investigations [32] showed that the analysis of a large number of mono- and dibasic acids is more efficient if n-propyl esters are chroniatographed instead of methyl esters. In this method, the esters were obtained by interaction with n-propanol and boron trifluoride, and separation was carried out on a column packed with 3% poly(ethylene glycol) or 3% silicone oil on Celite. The method for the industrial analysis for unsaturated polyesters is different from the preceding methods in that dibasic acids (methyl esters) and glycols are separated on a single column. The resin is first separated from the solvent (styrene) by re-precipitation from light petroleum [33] and the solid resin is re-esterified with sodium methoxide in methanol for 18 h. The resulting solution of glycols and methyl esters is analyzed directly by GC on a column (336 X 0.6 cm) packed with 20% GE silicone SF-96 on Fluoropak 80 at 1 10, 150 and 18OoC or with a programmed temperature increase from 110 to 180°C at 8"lmin. The GC of polyesters used in the production of polyurethanes has been developed [34]. The method permits the identification of polyesters in a mixture and the determination of the content of oxyethylene and oxypropylene groups. Polyesters are treated with a mixture of acetic anhydride and p-toluenesulphonic acid and the acetylation products are determined by GC. The results obtained by GC and nuclear magnetic resonance spectrometry are in good agreement. A method for the quantitative determination of hydroxyl groups in polymers has been proposed [ 3 5 ] ,based on the interaction of these groups with methylmagnesium iodide and subsequent quantitative determination of the methane released. In order t o separate the methane from the benzene or diethyl ether, which are used as solvents, a column (0.51nX 4 mm) packed with 10%N-methylpyrrolidone on alumina at 351°C was used, while for separating the nitrogen and methane a column (1 .O in X 6 mm) packed with molecular sieve 5 A was used. References p. 156
152
REACTION CC OF POLYMERS
The applications of reaction GC also include the analysis of mononuclear hydroxymethylphenols in the form of acetates in uncured resols [36] . The resol analysis was described in detail by Higginbottom et al. [37]. First, water was removed from the resol, then the hydroxyl groups of the polymer were converted quantitatively into acetates with the aid of acetic anhydride in the presence of pyridine. Removal of water was accompanied by partial loss of free phenol and formaldehyde, but. it completely prevented polymerization. Formaldehyde was present in the dehydrated resol in the form of a polyforrnal, HO * C6H4 CH2 * (OCH2), * OH, which, on acetylation, was stabilized in the form of an acetate, HO C 6 h CH2 (OCH2), OCOCH3, and produced several peaks on the chromatogram. Therefore, formaldehyde was removed in the form of a compound with pyridine bisulphide. The separation of hydroxymethylphenol acetates was carried out on a column (760 X 0.3 cig) filled with silicone SE-30 with a programmed temperature increase from 100 to 300°C at 5-6"C/min. The compounds formed were eluted from the column in the order of increasing molecular weight or, with polymers, of increasing boiling temperature. Benzyl acetate was used as internal standard. In determining 2,4,6-trihydroxymethylplienoltriacetate, it is better to use bis(4-acetoxy-3,5-dimethylplienyl)methaneas internal standard. Phenol derivatives can be chromatographed in the form of trimethylsilyl ethers on a column filled with DC-550 or di-n-butyl tetrachlorophthalate [38], and also in the form of trifluoroacetates [39] on a column filled with silicon oil plus tri-o-phenyl phenylphosphate (3: 1). An ingenious method for determining alkoxy groups in phenol esters by the hydrogenation method has been developed by Klesment and Kasberg [40]. The reaction chromatography of polymers, in which low-molecular-weight products are first formed by the action of the appropriate reagents and are then analyzed by GC, is an efficient method for investigating high-molecular-weight compounds with reactive bonds in the main polymer chain. As an example, we shall describe several chromatographic procedures in which hydrolysis is used in the analysis of the composition of various polymers. In the synthesis of linear polyesters, such as poly(ethy1ene terephthalate), a number of side reactions take place, for instance conversion of ethylene glycol to diethylene glycol. The inclusion of diethylene glycol in the polymer chain has an adverse effect on the properties of the polymer. In the GC determination of the amount of diethylene glycol in poly(ethy1ene terephthalate), the best results were obtained with the use of an inert column (200 X 0.6 cm) filled with 5% Carbowax 20M (30-60 mesh) on Haloport F at 170°C [41]. In this procedure, the polyester sample was saponified with sodium hydroxide for 30 min. These conditions did not ensure complete saponification, but as the saponification kinetics of ethylene glycol and diethylene glycol ether groups are almost identical, the proportions of the contents of the two glycols in the product and hence the ratio of the peaks of the substances analyzed are constant. Upon completion of the saponification reaction, the mixture was acidified with phthalic acid and methanol was added. The concentration of diethylene glycol was then determined from a previwsly plotted calibration graph. Later, a method was woiked out in which a metal column was used [42].The polymer was hydrolyzed under pressure f w 4 h at 230"C, then hydrolyzate was analyzed directly
-
- -
6
REACTION GC OF POLYMERS
153
with the use of benzyl alcohol as internal standard on a column (300 X 0.3 cm) filled with 10%Carbowax 20M on a diatomite support at 180°C. Despite the fact that during hydrolysis at 240°C the polymer decomposes to some extent, Janssen et al. [43] hydrolyzed the polymer sample at 250°C for 16 h, then tetraethylene glycol dimethyl ester (internal standard) was introduced and the mixture was separated on Carbowax a t 290°C. A simpler version for determining diethylene glycol in poly(ethy1ene terephthalate) involving decomposition of the sample with 85% hydrazine at 115"C, has been described [44], The analysis of polyamides by GC [45] was carried out by hydrolyzing the test samples in 6 N hydrochloric acid at 130°C for 24-48 h. The results showed the presence of dicarboxylic acids, hydrochlorides of w-amino acids and diamines in the hydrolyzate. In order to carry out the GC analysis, the active hydrogen atom in the amine and carboxyl groups was repIaced with a trimethylsilyl group by treatment with N,O-bis(trimethylsilylacetamide), thus making it possible to identify the compounds of the above three classes on a single column. The reaction of the dry hydrolysis products with the reagent was carried out under the dry nitrogen in a sealed tube for 2 h at 80°C. The dicarboxylic acids were also analyzed in the form of their methyl esters, for which purpose the hydrolyzate was treated with methanol plus p-toluenesulphonic acid. The high-volatility amines were analyzed in the free state; in order to do this, their hydrochlorides were treated with potassium hydroxide in methanol. The method for determining the composition of copolyamides [46] also includes depolynierization by hydrolysis. A polymer sample was hydrolyzed in 6 N hydrochloric acid. One portion of the hydrolyzate, containing amine hydrochlorides and free acids, was evaporated, esterified with a niethanolic solution of boron trifluoride and extracted with diethyl ether. The ether extract of the methyl esters was chromatographed on a column (200 X 0.6 cm) filled with 5% diethylene glycol adipate on Chromosorb W treated with an acid (60-80 mesh). Azelaic acid, which was used as the internal standard, was added prior to esterification. A second portion of the hydrolyzate was neutralized with sodium hydroxide in order to isolate the amines and convert dibasic acids into sodium salts. The free amines were extracted with n-butanol and chromatographed on a column filled with 10%Apeizon L deposited on glass beads. Both columns were heated with a programmed temperature increase from 100 to 220°C at S"C/min. The relative error of the determination was k 5%. The quantitative and qualitative determination of alkoxyl groups in acrylic copolymers can be achieved by taking advantage of the cleavage of the alkoxyl groups by a mixture of potassium iodide and orthophosphoric acid upon heating for 2 h to 200°C [47] . The alkyl iodides released are absorbed by n-hexane on cooling the trap to -75°C; they then are analyzed by GC. For polyacrylates, a method was devised in which the alcohols formed as a result of saponification of the polymer were analyzed on a colurnn (122 X 0.6 cni) filled with 23% Oronit NI-W on firebrick (42-60 mesh) [48] . The polymer sample was dissolved in tetrahydrofuran and saponified with an alcoholic solution of potassium hydroxide at 160°C for 4 h, then the contents were neutralized and chromatographed. This method was used to analyze decyl, lauryl and 2-ethylhexyl acrylates.
References p. 156
154
REACTION G C OF POLYMERS
Earlier work [49] dealt with hydrolysis of copolymers of trioxan and the glycolformyl of orthophosphoric acid with subsequent separation of the products on dodecyl phthalate or a silicone stationary phase at 150°C. Interaction with orthophosphoric acid was also used for determining the weight ratio of oxypropylene and oxyethylene groups in poly(propy1ene oxide) and poly(ethy1ene oxide) [ S O ] . The polymer sample reacted with the orthophosphoric acid in an inert atmosphere at 350°C at the chromatograph inlet, forming propionaldehyde and acetyldehyde, respectively. The percentage of oxyalkylene groups was proportional to the amount of the aldehyde formed. Hydrolysis and GC have been used for analyzing copolymers of cis- and trans-cyclohexanediol-1,2 [51 1 , diisopropyl esters of polyoxymethylene [52] ,cyano-containing polymers [53] and also other polyesters [54] and alkyd resins [55]. It should be noted that in many instances the method permits the determination not only of the initial monomeric compounds, but also of the distribution of the monomers in the copolymer. Thus, for instance, hydrolysis and combined GC nuclear magnetic resonance analysis have been used for determining the distribution of isomers in propylene oxide-maleic anhydride block copolymers [56] and propylene oxidecitraconic anhydride block copolymers [56, 571 prepared on different catalysts. Glycol esters were separated on a column filled with mercury(I1) chloride and Carbowax 20M on Chromosorb CL (60-80 mesh). A similar method was used for establishing the distribution of monomers in polysulphite esters obtained by copolymerization of propylene oxide and sulphur dioxide on different catalysts [58]. In analytical practice, use is also made of polymer cleavage (as a result of a reaction with hydrogen bromide) with subsequent analysis of the bromide formed. For determining the composition of copolymers of methyl methacrylate, ethyl acrylate and butyl maleinate [59, 601, the combined uses of Zeisel’s method and GC has been suggested. At first [59], the method was intended for determining the composition of copolymers of methyl methacrylate with ethyl acrylate that contained less than 10%of the latter. The alkoxyl groups of the copolymer were converted into the corresponding alkyl iodides with the aid of hydriodic acid in a phenol solution, then the iodides were isolated and chromatographed on a column containing dinonyl phthalate on Celite at 150°C. Methylene chloride and ethylene chloride were used as internal standards for methyl and ethyl iodides, respectively. Later [60], in order to determine butyl maleate, which is also present in the copolymer, the analysis was carried out on a column (300 X 0.6 cni) filled with di-2-ethylhexylsebacate on firebrick at 70°C. This method was also used successfully for analyzing the weight ratio of oxyethylene and oxypropylene groups in alkylene oxide polymers [61, 621 . A polymer sample (20 mg) was converted into the dibromide by interaction with excess of a 45-50% mixture of acetic and hydrobroniic acids at 150°C for 2 h [61]. The bromides formed were dissolved in carbon disulphide and analyzed on a glass column (90 X 0.4 cm) filled with 30% silicone E-301 on Celite (30-60 mesh) at 65°C. Using the ozonation reactiw with subsequent GC analysis of aldehydes and acids, one can determine the micro-structure of rubbers [63] .
REACTION GC OF POLYMERS
155
On interaction with BF30(C2H5)2,methylsiloxane form fluorosilanes, the GC analysis of wluch yields the ratios of the groups (CH3)3Si, (CH3)*Si and CH3Si in the polymers [64] . The disadvantage of this method is that the time required t o complete the reaction at 70°C is 96 h. The fluorosilanes formed were cooled with a mixture of dry-ice and acetone, then dissolved in diethyl ether and analyzed on a capillary column (4600 X 0.05 cm) filled with silicone SE-30, and a column (122 X 0.6 cm) filled with 16.6%squalane on Teflon-6 at 35°C. In this reaction, the ethylsiloxane groups are converted into C2H5SiF5, which is eluted simultaneously with (CH&SiF*. Therefore, in practice the method is restricted t o the investigation of methylsiloxane polymers. Vinyl groups of silicone rubbers, after interaction with orthophosphoric acid (in order t o convert the vinyl groups into ethylene) [65] , are also determined chromatographically on a column (1 12 X 0.6 cm) filled with alumina a t 65°C. A modification of this method was described by Krasikova and co-workers [66,67]. The structural analysis of polysiloxanes by GC and thermal analysis was developed by Franc et al. [68]. Note that in trying t o establish the structure of a polymer, it is also advisable t o use data on its elemental composition. Methods of elemental analysis involving the use of GC have been described [8, 69, 701. The reaction on polyniers t o physical factors such as radiolysis and ultraviolet (W) light, coupled with subsequent GC analysis of the volatile decomposition products, is an additional means for characterizing polymers. The radiation-chemical method can be used for the quantitative identification of polymers. Berezkin et al. [71] studied the dependence of the range of gaseous radiolysis products on the polymer structure in the series polyethylene, polypropylene, polyisobutylene, which differ, among other things, in the concentrations and positions of the methyl groups. A weighed polymer sample was placed in a glass ampoule, which was evacuated t o mni, sealed and irradiated with y-rays (from a cobalt-60 source) at a dose rate of 1.7 1OI6 eV/g sec. The gaseous radiolysis products were analyzed chronlatographically. The method has a high sensitivity t o hydrocarbon substituents in the main chain. The sensitivity t o lateral branchings in the main chain permits, in particular, low- and high-pressure polyethylenes t o be distinguished. The effect of radiation on copolymers of vinyl acetate with ethylene makes it possible t o determine the quantitative composition of the copolymer. When a polymer sample is subjected t o 100 Mrad of y-radiation (721 , low-molecular-weight hydrocarbons, carbon monoxide, carbon dioxide and hydrogen are formed. The amount of carbon monoxide not detected in the decomposition products of pure polyethylene is proportional t o the vinyl acetate content in the copolymer. The accuracy of the determination is 1%. In investigations on the degradation of polymers under the effect of electrons [73], it was shown that in branched polyethylene, ethyl and butyl radicals are located after each 100 carbon atoms. On irradiation of polypropylene, methane is formed, which indicates the absence of recombination of the methyl radicals under the conditions used. Low-volatility compounds can be analyzed by the photodecomposition method [74, 751 A mercury-saturated sample was placed in a silica capillary tube, which was evacuated and sealed. The sample was then irradiated from a mercury source. The chroinatograms obtained after irradiation are simple and reproducible. The method can be used
-
*
References p. 156
156
REACTION GC OF POLYMERS
successfully in standard determinations, and also for estimating the photodecomposition stability of the polymer. The combination of photodecomposition with GC is used for estimating UV adsorption in polymers [76]. Samples of polymer film in a silica vessel were irradiated from a standard UV lamp, then the degree of decomposition of the film was estimated by analyzing, at definite time intervals, the gaseous decomposition products. A column (200 X 0.635 cm) filled with poly(propy1ene glycol) on Chromosorb W at 100°C was used. The chromatograms of films of acrylonitrocellulose containing 54-55% of poly(methy1 methacrylate), 24-26% of dinitrocellulose, 19-2 1% of dioctyl phthalate and 1% of absorber have seven main peaks, varying in height. The decomposition of the polymer is proportional to the efficiency of the absorber. Of the several absorbers investigated, 2,2'-dihydroxy-4-methoxybenzophenone (Cyasorb UV-24) was the most efficient. Thus, the investigation and analysis of polymers by reaction GC make it possible to determine a number of important characteristics of high-molecular-weight compounds: the proportions of the initial monomeric compounds, the distribution of monomers in the polymer chain, the content of the separate functional groups, etc. Unfortunately, the development of these methods has not been given sufficient attention until recently. The level of application of reaction GC methods in polymer analysis is considerably lower than their apparent potential. In our opinion, one of the factors restricting the application of chromatographic methods is the lack of systematic manuals on the use of gas chromatography in the functional group analysis of organic compounds, including polymers.
REFERENCES 1 L. McLaren, M. N. Myers and J. C. Giddings, Science, 159 (1968) 197. 2 G. W. Rijnder, J. P. A. Bleumer and M. van Krevelen, in K. V. Chutov and K. 1. Sakodynsky (Editors), Uspekhi Khromatografii (Advances in Chromatography), Nauka, Moscow, 1972, p. 65. 3 Z. Deyl, K. Macek and J. Jan& (Editors), Liquid Column Chromatography - A Survey ofModern Techniques and Applications, (Journal of Chromatography Library, Vol. 3), Elsevier, Amsterdam, 1975. 4 J. J. Kirkland (Editor), Modern Practice o f Liquid Chromatography, Wiley-Ipterscience, New York, London, Sydney, Toronto, 1971. 5 S. G. Perry, R. Amos and P. 1. Brewer, Practical Liquid Chromatography, Plenum Press, New York, London, 1972. 6 S. Siggia (Editor), Instrumental Methods of Organic Functional Group Analysis, Wiley-Interscience, New York, London, Sydney, Toronto, 1972. 7 V. G. Berezkin, V. S. Tatarinsky, M. V. Palyanova and M. M. Fedyachkin, Usp. Khim., 4 3 (1974) 2088. 8 V. G. Berezkin, Analytical Reaction Gas Chromatography, Plenum Press, New York, 1968. 9 N. D. Cheronis and T. S. Ma, Organic Functional Group Analysis by Micro and Semimicro Methods, Interscience, New York, London, Sydney, 1964. 10 L. S. Ettre and W. H. McFadden (Editors), Ancillary Techniques of Gas Chromatography, WileyInterscience, New York, London, Sydney, Toronto, 1969. 11 L. V. Kolesnik and M. N. Chuniachenko, Izv. Akad. Nauk SSSR, Ser, Khim, (1969) 2107. 12 S. Zeisel and R. Fanto, Z. Anal. Chetn, 4 2 (1903) 549. 13 G. Castello, G. D'Amato and E. Biagini,L Chromatogr., 41 (1969) 313.
REFERENCES
157
14 C. L. Hanson and R. C. Smith,Anal. Chem., 44 (1972) 1571. 15 V. G. Berezkin, G. L. Groniova and T. P. Golitsyna, Vysokomol Soedin.. Ser. A, 17 (1975) 1177. 16 J. B. Stead and A. H. Hindley, J. Chromatogr., 42 (1969) 470. 17 M. Hellman and L. A. Wall, in G. M. Kline (Editor), Analytical Chemistry ofPolynzers, Part III, Identification Procedures and Chemical Analysis, Interscience, New York, London, 1963. 18 J. Franc and F. Mikes, J. Chromatogr., 26 (1967) 378. 19 G. G. Esposito and M. H. Swann, Anal. Chem., 33 (1961) 1854. 20 G. G. Esposito, Anal. Chem., 34 (1962) 1173. 21 K. Assmann, 0. Serfas and G . Geppert, J. Chromatogr., 26 (1967) 495. 22 R. E. Wittendorfer, Anal. Chem., 36 (1964) 930. 23 G. G. Esposito and M. H. Swann, Anal. Chem., 34 (1962) 1048. 24 L. 1. Gerasiniova, V. R. Zlobina and G. A. Ermolayeva, Lakokrasoch. Muter. Ikh. Primen., No. 2 (1970) 58. 25 J. K. Haken, J. Gas Chromatogr., 2 (1964) 263. 26 S. Dal Nogare and R. S . Juvet, Anal. Chem., 34 (1962) 35P. 27 C. W. Gehske and D. F. Goerlitz, Anal. Chem., 35 (1963) 76. 28 1. Hornstein and P. F. Growe, Anal. Chem., 33 (1961) 310. 29 0. Mlejnek, Chern. Prfim, 14 (1964) 586. 30 S. Jankowski and P. Garner, Anal. Chem., 37 (1965) 1709. 31 R. A. L. Paylor, R. Feinland and N. H. Conroy, Anal Chem., 40 (1968) 1358. 32 A. J. Appleby and J. E. Mayne, J. Gas Chromatogr., 5 (1967) 266. 33 D. F. Percival, Anal. Chem., 35 (1963) 236. 34 K. Tsuji and K. Konishi, Analyst (London), 99 (1974) 54. 35 K. V. Alekseyeva and L. P. Khramova, Zh. Anal Khim., 27 (1972) 163. 36 S. H. Rider and E. E. Hardy, Advan. Chem., 34 (1972) 173. 37 H. P. Higginbottom, H. M. Culbertson and J. S. Woodbrey, Anal. Chem., 37 (1965) 1021. 38 S. H. Lander, P. Pantages and F. Wender, Chem. Ind. (London), (1958) 1664. 39 A. T. Shulgin, Anal. Chem., 36 (1964) 920. 40 I. Klesment and A. Kasberg, Microchim. Acta, (1967) 1136. 41 D. R. Gaskill, A. G. Chasar and C. A. Luchesi, Anal. Chem., 39 (1967) 106. 42 L. H. Polder, Anal Chem., 40 (1968) 228. 43 R. Janssen, H. Ruysschaert and R. Vroom, Makromol. Chem., 77 (1964) 153. 44 H.-D. Dinse and E. TuEer, Faserforsch. Textiltech., 21 (1970) 205. 45 H. Tengler, Plastverarbeiter, 22 (1971) 329. 46 A. Anton, Anal. Chem., 40 (1968) 11 16. 47 V. R. Zlobina, N. P. Zvyagintseva, L. 1. Gerasiniova and T. A. Ermolayeva, Lakokrasoch. Muter. Ikh. Primen.. No. 6 (1972) 55. 48 J. G. Gobler and E. P. Samsel, SPL Trans., 2 (1962) 145. 49 H. Cherdron, L. Hohr and W. Kern, Angew. Chem., 73 (1961) 215. 50 E. J. Bockowski and H. M. Heresh, 3rd Middle Atlantic Regional Meeting of the American Chemical Society, February, 1968. 5 1 R. Nowicki, Bull. Acad. Pol. Sci. Ser. Sci Chim., 11 (1968) 557. 52 E. Klein, J. Smith and R. J. Eskert, J. Appl. Polym. S c i , 7 (1963) 383. 53 D. G. Val’kovsky, V. N. Robas, S. V. Rogozhin, A. M. Polyakova, V. V. Korshak, K. A. Mager and V. N. Semintsev, Zavod. Lab., 34 (1968) 528. 54 0. Mlejnek, Chem. M m , 1 3 (1963) 105. 55 J. K. Haken,Aust. Paint J., 13 (1967) 11. 56 R. J. Kern and J . Schaefer, J. Amer. Chem. Soc., 89 (1967) 6. 57 J. Schaefer, R. J. Katnik and R. 3. Kern, Macromolecules, 1 (1968) 101. 58 J. Schaefer, R. J . Kern and R. J. Katnik, Macromolecules, 1 (1968) 107. 59 J. Haslain, J. B. Hamilton and A. R. Jeffs,Analyst(London), 83 (1958) 66. 60 D. L. Miller, E. P. Sanisel and J . G. Cobler, Anal. Chem., 33 (1961) 677. 61 A. Mathias and N. Mellor, Anal. Chem.. 38 (1966) 472. 62 M. Filipska, Z. Hippe, T. Krryjanowska and T. Stazeczek, Chem. Anal. (Warsaw), 12 (1967) 39.
158
REACTION GC OF POLYMERS
63 G. M. Akhmedli and A. N. Perelman, Vysokomol. Soedin., 8 (1966) 61. 64 G. W. Heylmun and J. E. Pikula,J. Gas Chromatogr., 3 (1965) 266. 65 G. W.Heylmun, R. L. Bujarski and H. B. Bradley,J. Gas Chromatogr., 2 (1964) 300. 66 V. M. Krasikova and A. N. Kaganova, Zh. Anal. Khim, 25 (1970) 1409. 67 V. P. Mileshkevitch, V. M. Krasikova, A. H. Kachanova, A. V. Kerlin and T. N. Pratova, Author’s Certificate, No. 395,769, Applied 6.7.71; published 25.1.74. 68 J. Franc, K. PlaEer and F. Mike& Collect. Czech. Chem Commun., 32 (1967) 2242. 69 F. Salzer, Microchem J.,16 (1971) 145. 70 H. Kelker, in H. G. Struppe (Editor), Aspects of Gas Chromatography, Akademie-Verlag, Berlin, 1971, p. 37. 71 V. G. Berezkin, Yu. A. Kalbanovksy and E. A. Kyazimov, Vysokomol. Soedin.,Ser. A , 9 (1967) 2566. 72 R. M. Kamath and A. Barlow, Anal. Chem., 37 (1965) 1266. 73 R. Salovey and J. V. Pascale, J. Polym. Sci, Part A-2, (1964) 2041. 74 R. S. Juvet, 11.and L. P. Turner,Anal. Chew., 37 (1965) 1464. 75 R. S. Juvet, Jr., R. L. Tanner and J. C. Y. Tsao, J. Gas Chromatogr., 5 (1967) 15. 76 H. C. Su and J. L. Cameron, Anal. Chem., 39 (1967) 949.