Polyphenyleneethyl-polystyrene graft copolymers containing functional groups

2904

H . S . KOLESNIKOVet al.

tension, dipole moment and electrical conductivity) influences the reduced viscosity of polyamidocarbonates. Obviously in the case considered here the main influence in this respect will be the electronegativity of the solvent. CONCLUSIONS

(1) Polyamidocarbonates based on di-(4-aminophenyl)carbonate and the dichlorides of terephthalic and isophthalic acids have been synthesized b y interfacial polycondensation. The possibility of using the hydrochloride of di-(4-aminophenyl)carbonate for the synthesis in question has been proved. (2) The main mechanisms of interracial polycondeusation have been studied, and the optimum conditions for the process have been found. Translated by R. J. A. HEI~DRY

REFERENCES

1. H. S. KOLESNIKOV, O. V. SMIRNOVA and V. N. LAMM, Vysokomol. soyed. All: 905, 1969 (Translated in Polymer Sei. U.S.S.R. 11: 4, 1022, 1969) 2. L. B. 80KOLOV and T. V. {~UDAKOVA,USSR Pat. 121934, 1958; Byull. Izob. No. 16, 1959 3. V. N. LAMM, O. V. SMIRN0VA and H. S. KOLESNIKOV, Trans. Mendeleyev Chem.Tech. Inst., Moscow, No. 57, 102, 1968 4. French Pat., 1353461, 1964; Chem. Abstr 61: 574, 1964 5. Chemical handbook (Russ. Spravochnik khimii). Vol. II, Goskhimizdat, 964, 694, 1964

POLYPHENYLENEETHYL-POLYSTYRENE 6~RAFT COPOLYMERS CONTAINING FUNCTIONAL GROUPS* I-I. S. KOLESNIKOV (dec.), A. S. TEVLINA, A. T. DZHALILOV and T. S. •ORGIS D. I. Mendeleyev Chemico-technological Institute, Moscow (Received 26 November 1968)

SYNTHESIS of graft copolymers using chain transfer through the polymer normally produces mixt, ures which contain the corresponding homopolymers as well as the graft copolymer. Elimination of these homopolymers is often a complex problem because of the similar solubilities of graft copolymers and homopolymers. This problem becomes easier when graft eopolymers are synthesized, the components of which markedly differ from each other in solubility. Graft copolymers * Vysokomol. soyed. All: No. 11, 2554-2561, 1969.

Polyphenyleneethyl-polystyrene graft copolymers

2905

of the diphyl type are of this kind and are formed from hydrophilic and hydrophobic polymers. A description is given of graft copolymers of the diphyl type, which incorporate chains of polymethacrylic acid and a polyester of ~o-hydroxypelargonic [1], polyacrylic acids, polyphenyleneethyl [2], etc. However, synthesis of graft copolymers of the diphyl type is normally difficult by the method of chain transfer through the polymer, owing to the low compatibility of the raw materials. It is therefore of interest to obtain graft copolymers of the diphyl type by grafting a hydrophobic polymer to another polymer, which is also hydrophobic, but contains functional groups further conversion of which produces the hydrophilic polymer. We synthesized a graft copolymer by grafting polystyrene to chloromcthylated polyphenyleneethyl. During further amination of the graft copolymer the unreacted chloromethylated groups form salts of a quaternary ammonium base. A graft copolymer of the diphyl type is formed as a result, which contains polystyrene, a hydrophobic polymer, and aminated polyphenyleneethyl, a hydrophilic polymer. The process was carried out as follows

,~ ~

BP

CH2-C H 2 - - ~ CH2--CH2--~ + CH25 CH2CI CH2CI N CH2Cl

F

~H2 ~CH M2

/N Cl-

Polystyrene was grafted to chloromethylated polyphenyleneethyl by chain transfer. It is well known that in graft copolymerization by chain transfer the efficiency of grafting depends on the presence of mobile groups of atoms in the main polymer and increases with increased mobility of these groups or atoms. It was also established that the chlorine atoms in chloromethyl groups of aromatic nuclei are very mobile, which accounts for many conversions of these groups in organic synthesis. Consequently, the presence of the chloromethyl group in the copolymer during graft copolymer synthesis by chain transfer increases the constant of chain transfer through this polymer, and thus increases the graft copolymer yield.

H. S. KOLESNIKOVet

2906

al.

The graft copolymer of chloromethylated polyphenyleneethylwith polystyrene was synthesized by polymerization of styrene with ehloromethylated polyphenyleneethyl of molecular weight 13,000, which had been previously dissolved in styrene. Benzoyl peroxide (BP) was used as initiator. Copolymerization was carried out by a bulk method in ampoules which were filled with argon after the reaction mixture had been put in, sealed and placed in a thermostat. After the reaction the ampoules were cooled and the contents dissolved in benzene. The graft copolymer was precipitated from solution by isopropyl alcohol and dried i n v a c u o at 40 °. It is well known that the efficiency of grafting in graft copolymerization by chain transfer through the polymer is influenced by various factors. We examined the effect of factors such as initiator concentration, reaction temperature and reaction time on graft copolymerization of chloromethylated polyphenylene ethyl with polystyrene. An important factor which influences graft copolymerization by chain transfer through the polymer is the type and amount of initiator. It is noted [3] that benzoyl peroxide is the most effective initiator in graft copolymerization by chain transfer through the polymer; with the increase of initiator concentration the efficiency of grafting increases, Results shown in Table 1 indicate that with increased initiator concentration the graft copolymer yield increases. This indicates that graft copolymers are mainly formed as a result of the direct attack on the main chain of chloromethylated polyphenyleneethyl by radicals initiating the reaction to produce macro-radicals which initiate styrene polymerization with formation of branches. TABLE

1.

EFFECT

COPOLYMERIZATIOI~

OF

INITIATOR

(REACTION

CONCENTRATION

CONDITIONS:

ON

GRAFT

REACTION

TIME

8 h r GRAVIMETRIC RATIO OF C H L O R O M E T H Y L A T E D P O L Y P H E I ~ r L E N E E T H Y L : S T Y R E N E I ~ T H E I N I T I A L M I X T U R E 3 0 : 701

Graft Cl conCl conBP concentra- copolymer tent in tent in tion, wt. ~o of yield (GC), GC before GC after styrene ~/o amination, amination % % 0"5 1 2 5

42 58 64 65

8.1

7.0 6.2 4.3

3.3 3.1 2.9 3.1

Polystyrene content in GC,

65 66 69 66

Further experiments were carried out with a BP concentration of 2 % of the weight of styrene. It should be noted that a relatively high initiator concentration on the one hand increases grafting efficiency and, on the other hand, enables graft copolymers of low viscosity to be synthesized. This is important in the

Polyphenyleneethyl-polystyrene graft copolymers

2907

subsequent chemical conversion of polymers and copolymers since chemiea~ conversions of high viscosity polymers are normally accompanied by secondary reactions which in most cases result in the formation of three-dimensional crosslinked products. Another important factor affecting graft copolymerization by chain transfer through the polymer is reaction temperature. The reaction rate of chain transfer TABLE 2. EFFECT OF REACTION TEMPERATURE ON GRAFT COPOLYMERIZATION (REACTION CONDITIONS: AMOUNT OF B P , 2 ~ OF THE WEIGHT OF STYRENE~ REACTION TIME 8 hr, GRAVIMETRIC RATIO OF CHLOROMETHYLATED POLY'PHENYLENEETHYL : STYRENE IN THE INITIAL MIXTURE 30 : 70)

Reaction t e m p . °C

GC yield,

%

C l c o n - :i C l c o n t e n t in t e n t inGC beGC a f t e r fore arni- a m i n a t i o n , nation, :

% 60 80 95 125

53 62 63 68

11.5 8"1 6"2 2"9

Polystyr e n e cont e n t in

GC,

]

i

3.2 2.9 2.9 2.6

76 69 69 74

T A B L E 3. E F F E C T OF R E A C T I O N TIME ON G R A F T C O P O L Y M E R I Z A T I O N

(REACTION CONDITIONS: B P CONCENTRATION 2 ~o OF T H E W E I G H T OF STYRENE~ R E A C T I O N T E M P E R A T U R E OF

CHLOROMETHYLATED

THE INITIAL MIXTURE

Reaction time,hr

GC yield,

%

2 5 8

12

59 61 63 63

9 5 °, GRAVIMETRIC RATIO

FOLYPHENYLENEETHYL:STYRENE

C1 conC1 cont e n t int e n t inGC beGC a f t e r fore a m i - a m i n a t i o n , % nation, 9"5 6"9 5"7 3"0

IN

30 : 70)

3.2 3.2 2.9 2.7

Polystyrene cont e n t in

GC,

67 67 69 73

through the polymer increases with temperature to a greater extent than the reaction rate of chain extension since the acbivation energy of chain transfer is higher than the activation energy of chain extension. For this reason graft copolymerization is normally effeeted by chain transfer through the polymer at

2908

H. So KOLESl~'IKOVet al.

relatively high temperatures. It follows from Table 2 that during grait copolymerization of chloromethylated polyphenyleneethyl with styrene the graft copolymer yield increases with reaction temperature. Subsequent experiments were carried out at 95 °. It was found that during graft copolymerization of ehloromethylated polyphenyleneethyl with styrene the gra/t copolymer yield increases with lo~ger reaction time (see Table 3). Investigations established the following reaction conditions for graft eopolymerization of ehloromethylated polyphenyleneethyl with polystyrene: amount of BP, 2% of the weight of styrene, reaction temperature 95 °, reaction time 8 hr. -AD.2,~n2 ,,., 2"0

2"#

f2

1"6

6~8

24

32

#0 m , voL %.

48

0

I

2#.

32

#0 ~,8 m, vol. %

FIG. 1. Integral (a) and differential (b) turbidimetrie titration curves of chloromethylate4 polyphenyleneethyl (CPPE)-polystyrene graft copolymers (GC). CPPE content in GC (~): •--20, 2--30, 3--40. The chloromethylated polyphenyleneethyl - polystyrene graft copolymer synthesized under these conditions is a light brown powder, readily soluble in benzene, dioxane and other organic solvents. The graft copolymer which contained chloromethyl groups was aminated with pyridine. Amination was carried out in a three-necked flask, equipped with a stirrer and reflux condenser and placed in a water bath at 50 °. The 10% solution of the chloromethylated polyphenyleneethyl polystyrene graft copolymer in dioxane and pyridine, used in a two-fold molar excess in relation to the content of chloromethyl groups in the graft eopolymer, was placed in the flask. Amination was carried out for 6 hours. After amination the residue was separated~ treated with petroleum ether until the odour of pyridine disappeared and dried i n vacuo

Polyphenyleneethyl-polystyrenegraft copolymers

2909

at 40 °. The aminated graft copolymer thus obtained was then treated with benzene and water to eliminate the homopolymers. A diphyl type graft copolymer was obtained which consisted of an aminated polyphenyleneethyl main chain and polystyrene side branches. Table 4 shows the chief properties of diphyl type graft copolymers synthesized with varying chloromethylated polyphenyleneethyl contents in the initial mixture. It was of interest to study the dependence of properties of graft copolymers on the properties of homopolymers which constitute the main chain and the grafted branches. However, it was necessary first of all to ascertain whether the synthetic copolymers were graft copolymers, or a mixture of homopolymers. For this purpose we studied the molecular weight distribution (MWD) of synthetic graft copolymers by turbidimetric titration.

//•

28f1#

(z

5

1 2.81 lzt

f

20II"0

f06

12

0~1-02

t / lt i 30

#2

50

5# [

38

#6

m , vo[. %

Fro. 2. Curves of turbidimetric titration of a mechanical mixture containing 20 CPPE (a) and aminated graft copolymer (b): 1 - integral an4 2--differential curves. Figure la shows integral I~IWD curves of unaminated graft copolymers o f chloromethylated polyphenyleneethyl and polystyrene. The Figure shows that there are no inflexions on the integral curves of graft copolymers containing 20 t o 30% chloromethylated polyphenyleneethyl in the initial mixture (curves 1, 2), whereas there is an inflexion on the integral curve of the graft copolymer containing 40% chloromethylated polyphenyleneethyl (curve 3) in the initial mixture. Differential MWD curves shown in Fig. lb also indicate that in the case o f graft eopolymers containing 20 to 30% chloromethylated polyphenyleneethyl in the initial mixture (curves 1, 2), a homogeneous product, i.e. a pure graft copolymer is formed by the reaction and when the reaction is carried out with 400/o.

2910

H . S. KOLESNIKOV et a~.

chloromethylated polyphenyleneethyl in the initial mixture a heterogeneous product is formed, which proves the presence of an inilexion on the differential MWD curve. In this case some of the chloromethylated polyphenyleneethyl does not apparently react. Chain transfer through the chloromethylated polyphenyleneethyl takes place very readily. In fact, the constant of chain transfer by polystyrene radicals through benzyl chloride, which to some extent simulates chloromethylated polyphenyleneethyl, is 15.6 × 10-5 at 60°; this under the same conditions exceeds almost 100 times the chain transfer constant by polystyrene radicals through benzene molecules, ~hich is 0.18× 10.5 [4]. Consequently, even during graft copolymerization of chloromethylated polyphenyleneethyl with styrene the interaction of growing chains of polystyrene with chloromethylated polyphenyleneethyl macroradicals much more of ten results in reaction than interaction with polyphenyleneethyl, without CHIC1 groups. As a result of the reaction macroradicals are formed which initiate styrene polymerization. These macroradicals are also formed as a result of the interaction of chloromethylated polyphenyleneethyl maeromolecules with radicals formed during the decomposition of benzoyl peroxide. Polymerization of styrene initiated by polyphenyleneethyl macroradieals results in the formation of a graft copolymer. The absence of appreciable amounts of styrene homopolymer in products of graft copolymerization proves that maeroradicals are mainly formed as a result of the interaction of chloromethylated polyphenyleneethyl with radicals produced by the decomposition of benzoyl peroxide. The TABLE 4. PROPERTIES OF GRAFT COPOLYMERS

Content of chloromethylated polyphenyleneethyl in the initial mixture, 20

30 40 50

GC yield, %

62 58 56 46

Cl conC1conPolystytent in tent in rene conGC GC before tent in after amination GC, amination % %

2.7 3.0 5.5 10

2.6 2.8 3.7 7.7

79 72 62 21

possibility is not excluded that homopolystyrene macroradicals recombine with polystyrene radicals, which are side branches of the graft copolymer. The interaction of growing homopolystyrene radicals with chloromethyl groups of chloromethylated polyphenyleneethyl appears to be possible at the early stage of chain extension, resulting in the formation of low molecular weight polystyrene, which
Polyphenyleneethyl-polystyrene graft copolymers T A B L E 5. S O L U B I L I T Y OF G R A F T C O P O L Y M E R S

Chloromethyla~ed polyphenyleneetyl

Solvent, Benzene Methanol Dimethylformamide Water Benzene : methanol (hl) Benzyl alcohol

GC) AND

Aminated polyphenyl eneethyl

Polystyrene

2911

HOMOPOLYMERS

GC before GC after amination amination

d

n

d

d

n

n

n

d

d

n

d d d

n

n

n

n

n

n

n

n

d

d

d

2qote: d--dissolves, n--does not dissolve.

T h e absence of h o m o p o l y s t y r e n e from p r o d u c t s o f graft c o p o l y m e r i z a t i o n is confirmed b y the fact t h a t p u r e h o m o p o l y s t y r e n e was n o t f o u n d a f t e r amination of the g r a f t copolymer in fractions soluble in benzene. F r a c t i o n s soluble in benzene contain nitrogen and chloride ions, and a p p a r e n t l y r e p r e s e n t a g r a f t copolymer with a low c o n t e n t of a m i n a t e d c h l o r o m e t h y l a t e d p o l y p h e n y l e n e e t h y l . qki,, I

dl/g

-

1

12

¢2_1

10

0"8

8

0#

O

2 0.4

o.o

c,g/al

'

'dq'

'

'

'1'2

¢5" FIG. 3

Fro. 4

Fro. 3. Dependence of kinematic viscosity on concentration: 1--aminated graft copolymer (AGC)containing 20yo CPPE in the initial mixture, 2--AGC containing 3 0 ~ CPPE, 3--AGC containing 4 0 ~ CPPE, 4--aminated polyphenyleneethyl. FIo. 4. Dependence of (t/sp/c)-1 on ~/c (symbols are the same as for Fig. 3). Figure 2a shows integral and differential ~ W D curves of a mechanical m i x . t u r e containing 2 0 % c h l o r o m e t h y l a t e d p o l y p h e n y l e n e e t h y l and 8 0 % polystyrene; the inflexion on t h e integral curve and t h e secood p e a k on t h e differential M W D curve p r o v e t h a t these samples are heterogeneous.

2912

H.

S.

et al.

KOLESNIKOV

After amination of the graft copolymer and subsequent treatment with benzene and water a graft copolymer is formed free from homopolymers, as confirmed by the conventional nature of the integral curve and the one maximum on the differential MWD curve (Fig. 2b). Diphyl type graft copolymers are characterized by their relation to organic solvents. These eopolymers normally dissolve in mixtures of polar and non-polar solvents. Table 5 indicates solubility results of a diphyl type graft copolymer synthesized by the authors. Comparative results are given of the solubility of homopolymers and a chloromethylated polyphenyleneethyl-polystyrene graft copolymer. The graft eopolymer which consists of aminated polyphenyleneethyl and polystyrene, i.e. contains both polar and non-polar polymers, is insoluble both in polar and non-polar solvents. This graft copolymer dissolves in a methanol-benzene mixture (1 : 1), i.e. in the mixture of polar and non-polar solvents and in benzyl alcohol, the molecules of which can be regarded as molecules containing residues of polar and non-polar solvents. See also another paper [1] describing the solution of diphyl type graft copolymers in benzyl alcohol. The graft copolymer synthesized is readily soluble in dimethylformamide, in which both polystyrene and the product of amination of chloromethylated polyphenyleneethyl dissolve readily. 28

l

¢ 5

/

20

-~.~2

/ 60

100

I

I

I

140T,°C

FIG. 5. Temperature/deformation curves: /--polystyrene, 2--CPPE, 3--CPPEpolystyrene graft copolymer (20 ~ CPPE), 4-- product of amination of chloromethylated polyphenyleneethyl, 5--AGC obtained from a copolymer which had been synthesized from an initial mixture containing 20~ CPPE. It was of interest to study the behaviour of solutions of synthetic graft copolymers in dimethylformamide. It is known [5] that the dependence of kinematic viscosity on concentration for polyelectrolytes in non-ionizing solvents

Polyphenyleneethyl-polystyrenegraft copolymers

2913

(benzene, chloroform) is linear and in ionizing solvents (acetone, domethylformamide, methauol) is represented by a concave curve. Figure 3 shows the dependence of kinematic viscosity on the concentration of solutions in dimethylformamide for synthetic graft copolymers with varying aminated polyphenyleneethyl contents and for products of amination of chloromethylatcd polyphenyleneethyl. This Figure indicates that the kinematic viscosity increases in proportion to the dilution of solutions both for graft copolymers and for the amination product of chloromethylated polyphenyleneethyl. It is interesting to note that the dependence of (t/sp/c)-i on x/c for synthetic graft copolymers and for the amination product oi chloromethylated polyphenyleneethyl in dimethylformamide solution is linear (Fig. 4). This proves that the empirical equation of Fuoss and Strauss [6], which describes the behaviour of aqueous polyelectrols~te solutions is also valid for anhydrous polyelectrolyte solutions. We carried out a thermomechanical study of synthetic graft copolymers. The temperature/deformation curves shown in Fig. 5 were recorded in a Zhurkov device (load 1.5 kg/cm 2, period oi loading 10 sec). Comparative temperature/deformation curves were also obtained for homopolymers. Figure 5 shows that the softening point of synthetic graft copolymers and homopolymers is low, 65-70°C. This is due to the low molecular weight (t/kin) of synthetic copolymers and polymers. For the products of amination of chloromethylated polyphenyleneethyl and a graft copolymer the flow temperatures are somewhat higher than the flow temperatures of the corresponding chloromethylated derivatives, which is apparently due to the additicn of strong polar p)~idine groups to the macromolecules. CONCLUSIONS

(1) A diphyl type graft copolymer was synthesized by grafting styrene to chloromethylated polyphenyleneethyl, followed by amination. (2) A study of molecular weight distribution of the product shows that the diphyl type synthetic graft copolymer, after appropriate treatment, is free from homopolymers. (3) The solubility of the graft copolymer and the behaviour of the graft copolymer solution in dimethylformamide were investigated. Translated by E. SEMERE

REFERENCES

1. H. S. KOLESNIKOV and TSZEN-KItAN-MIN', Vysokomol. soyed. 2: 1870, 1960 (Not translated in Polymer Sci. U.S.S.R.) 2. A. E. CItUCItIN, Dissertation, 1966 3. U. BERLENT and A. HOFMAN,Privitye i block-copolimery (Graft and Block Copolymers). Izd. inostr, lit., 1963 4. S. N. BAMFORD,et al., Kinetika radikal'noi polimerizatsii (Kinetics of Radical Polymerization). Izd. inostr, lit., 1961

2914

A.G. RYABUKHIN

5. V. G. ALDOSHIN and S. Ya. FRENKEL', Vysokomol. soyed. 2: 347, 1960 (Not translated in Polymer Sci. U.S.S.R.) 6. R. FUOSS and J. STRAUSS, J. Polymer Sci. S: 246, 1948

KINETICS OF THE REACTION OF PHENOL WITH FORMALDEHYDE IN DIFFERENT MEDIA* A. G. I~YABUKHIN Kurgan Institute of Mechanical Engineering (Received 26 November 1968)

THE reaction of phenol with formaldehyde using acid or basic catalysts yields various products. Thus, in an acid medium thermoplastic phenolformaldehyde resins, and in an alkaline medium low molecular weight phenolic alcohols are formed which m a y subsequently harden [1-6]. I n spite of the extensive use of phenol formaldehyde resins the kinetics of production have not been sufficiently studied [7-11]. Let us examine the reaction of phenol with formaldehyde as successive processes of formation of methylol and methylene phenol derivatives according to equations of the type: C6H~OH+CHzOk-!-~Cell, (OH) CH~OH

(A)

CsH, (OH)CH2OH-FC6HsOH~-*CeH, (OH)--CH,--CsH,0H~-H~O

(B)

The reaction of phenol with formaldehyde according to an equation type A may result in formation of mono-, di- a n d trimethylol derivatives. Formation of a monomethylol derivative would be the first stage both in acid and alkaline media. The subsequent course of the reaction will be determined by the ratio of the rate consfiants kl and k2. When kl >/¢~ methylol derivatives will accumulate in the reaction, which results in the formation of low molecular weight phenolic alcohols. When kl~k2 the monomethylol derivatives will immediately react with the reactive centxes of free phenol, and this finally leads to the formation of polymers of linear structure. Let us examine reactions of type A and B from the point of view of formal kinetics. Let us use the following notation: a and b are the initial proportions of * Vysokomol. soyed. All: No. 11, 2562-2570, 1969.