Methods of investigation fractionation of aliphatic polyesters

METHODS OF INVESTIGATION FRACTIONATION OF ALIPHATIC POLYESTERS* G. I.

TARASOVA,

S. A. PAVLOVA and V. V. KORSHAK

I n s t i t u t e of Hetero-orgauie Compounds, U.S.S.R. A c a d e m y of Sciences

(Received 9 July 1971) MOLECULAR weight distribution (MWD) of polycondensation polymers was the object of a fairly large number of papers [1-10], which include M W D of aliphatic polyesters. However, these investigations mainly concern the fractionation of oligomer polyesters. A s t u d y was m a d e [3-5] of MWD b y a method of eluent, precipitation [7-9] and gel-permeation chroma. t o g r a p h y a n d b y extraction from thin films [10]. This paper seeks to examine M W D of aliphatic polyesters with high degrees of completion o f the reaction. Owing to the erystallinity of aliphatie polyesters fractionation b y precipit a t i o n [11, 12] is not effective enough. Selection of conditions of fractionation and evaluation of efficiency was therefore the first stage of determining MWD. XVo used aliphatic polyesters prepared from sebacic acid a n d decanediol (PESADD) and sebacic acid a n d hexanediol (PESAHD), prepared b y polycondensation in toluene at 130 ° with p-toluenesulpho-acid (p-TSA) as catalyst. The initial polyesters had the following properties: PESADD--[t/]sso toluene=0"6 dl/g, weight-average molecular weight M w = 28,600, a c i d number a . n . = 3 . 8 8 X 10-3g K O H / g PE, numerical average molecular weight Jtln = 14,400, degree of completion of the reaction being P = ( ~ f n - - M 0 ) / - ~ = 0.9895 (M0 is the molecular weight of a polyester unit). PESAHD---[tl]sso, toluene=0"77 dl/g, 2~w=46,500, a.n. = 1-98 × 10-* g K O H / g PE, P = 0 . 9 9 3 0 . R E S U L T S OF F I ~ A C T I O N A T I O N OF P O L Y E S T E R S S T U D I E D

Molecular weight characteristics

-'~/n × I0-~

~_w × 10-" _M, × 10-"

found

PESADD calculated* 26 fractions 25 fractions 130 fractions without a with a temperature temperature gradient gradient

144 286

MJM,, .MdM,,

1.985

~t/]~5o, toluene

O.600

180 315 376 1"75 1-20 0.597

112"5 313"5 387.6 2.78 1-20 0.560

124 325 483 2.60 1"485 0-560

* According to results of fractionation in the benzene-ethyl alcohol system.

? Same with temperature gradient.

* Vysokomol. soyed. A15: No. 4, 929-932, ]973. 1046

PESAHD

found

241"5 465 1.93 0.770

calculated t

208-6 405.6 552 1.94

1-36 0-670

Fractionation of aliphatie polyesters

1047

P E S A D D was fractionated by eluent chromatography [13] in a column of a l e n g t h l = 90 era, diameter d ~ 15 m m filled with quartz sand of particle size 0.25-0.32 ram. The rate of feeding the ehient was 0.5 ml/min. A polymer sample of 0.5-0.6 g dissolved in chloroform was mixed with sand and the solvent eliminated, the sand was then placed in the upper p a r t of the column. Molecular weights were determined by a method non-steady equilibrimn in a M 0 M G-120 ultracentrifuge (with extrapolation to infinite dilution). Acid nmnber was determined by potentiometric titration in a benzene-methanol (3 : 2) mixture.

/.0 EWi /'0-

o o 0

ZT~

0

0 o

°i

0.8

0"2

-

0 0

°oO

o

O.2

I

I 80

F~o. 1

I

I

100 Mw~ f O-a

0

I

20

1

I

6"0 I00 i~u . lO -a

Fee. 2

FIG. 1. MWD curves of P E S A D D : 1--fractionation with a temperature gradient for 30, 2 - - f o r 25 fractions and 3 - - w i t h o u t a temperature gradient for 26 fractions. Fee. 2. Plotting curve 1 of Fig. 1, acoording to the ordinal number of the fraction.

Benzene-ethanol (I) and tetrachlorethane (TCE)-heptane (II) systems were used for chromatographic fractionation. When using system I fractionation was carried out without (Fig. 1, curve 3) and with a temperature gradient (curves 1 and 2) in a column at a t e m p e r a ture of 45 ° in the upper and 22 ° in the lower part. When in the first case during fractionation with a temperature gradient the weight fractions were equal (curve 2), with repeated fractionation particular attention was given to fractionation in the los T. and high-molecular weight ranges (curve 2, Fig. 1). The Table and Fig. 1 give results of fractionation. I t should be noted t h a t plotting MWD curves with an arrangement of fractions according to exit from the column (Fig. 2) results in typical curves: first fractions are separated with increasing molecular weights and then the fractions are "reeireulated", i.e. with a further increase of t h e ordinal number of the fraction, molecular weight decreases. This effect was observed during: ehition of oligomer polyesters on silica gel [5], this being explained by adsorptive interactio~ of terminal hydroxyl groups with silica gel. Consequently, for polymers with hydroxyl a n d earboxyl end groups fractionation takes place not only according to molecular weight, but also according to the type of end groups. W i t h > 20 fractions and a temperature gradient along the chromatographic column, fractionation enables MWD curves to be obtained which are fairly close to the actual curves. An analysis of results of fraetionation by comparing average molecular weights measured and intrinsic viscosities with values calculated from experimental weight fractions w~ a n d

1048

G . I . TARASOVA e t a l .

molecular weights M~ of fractions

1

Z w,M

Z M--, (./~lrz is the z average molecular weight) showed (Table) t h a t with this n u m b e r of fractions conditions of fractionation have a m i n i m u m effect on the value of ~fw. I t should be noted t h a t i n every case the Mw value calculated appeared somewhat too high, compared with the value measured. A slight resolution in the low and high molecular weight part of the MWD curve results in a n increase of the ~/w value calculated and a reduction of the/~z value calculated (fract i o n a t i o n without a temperature gradient (Fig. 1, curve 3)). An increase in the n u m b e r of fractions in the initial part of MWD (Fig. 1, curve 2) enables the J~/, value calculated to approximate to the Mn value measured, and a n increase in frequency a n d in the high molecular weight part (Fig. 1, curve 1) markedly increases the value of Mz. I n the latter case results of fractionation are satisfactorily arranged on the F i e r y MWD curve (Fig. 1, curve 1) calculated for P = 0 . 9 8 9 5 . I t should be noted that with all the three fractionations of P E S A D D calculated coefficients of polydispersion Mw/Mn show a marked discrepancy from the mea. sured value. The value of Mz/Mw in the case of fractionation (curve 1, Fig. 1) is close to 1'495 which follows from the Flory MWI) when P----9895.

1.0~.

<>.....~...~oo

0"2-

3/ /'5~L

0"2 l~m. 3

0"0 d//<,.

/.01-

"~

"~

-~

~

~

f

..~ O .

.

.

.

.

.

~.

I ~'me , daq~ Fro. 4

~FIo. 3. F r a c t i o n a t i o n of PESADI) in system II: 1 - - t h e fractions are arranged according to increasing viscosities a n d 2--according to ordinal numbers. Fie. 4. Variation of t/Bp of P E S A D D in TCE over a period of time. F i g u r e 3 shows t h a t fractionation in system I I has a poor resolving power in the high molecular weight range and ~ wl[t]]t <[q]~t. A reduction in the overall viscosity of fractions ,is due to the decomposition of polyester in TCE which is colffirmed by a reduction of Ssp of the P E S A H D solution in TCE over a period of time (Fig. 4). A poor resolving power in the high molecular weight range is probably due to a reduction in the relation between polyester solubility a n d molecular weight a n d a n increase in eluent density in proportion to TCE ~ d d i t i o n (dTcv.-----1.6g/cm 3, dheptane~-0"68 g/era3).

Fractionation of aliphatic polyesters

1049

We therefore subsequently used a benzene-ethyl alcohol system for chromatographic fractionation. Under the conditions selected during fractionation of P E S A H D a "recirculat i o n " of fractions is also observed. Flory distribution calculated for a given degree of completion of the reaction, practically agrees with the experimental curve with fractions arranged in order of increasing molecular weight (Fig. 5). Z~4 /0

--

o

o

02 I

2O

I00 O0 Mw,10-a

FI(~. 5. MWD curves of P E S A t t D ; continuous l i n e - - M W D curve calculated according to Flory for P=0.9930, the points showing the experimental values. Consequently, for aliphatic polyesters of relatively high molecular weights belonging to readily crystallizing polymers, fractionation b y eluent chromatography enables us to obtain a MWD curve a n d molecular weight characteristics close to the actual values with the observation of conventional experimental conditions. Under o p t i m u m conditions a deviation between molecular weight characteristics calculated from fractionation data and measured values is under 15yo. F r o m these experimental data it m a y be concluded that MWD curves of polyesters obtained by equilibrium polycondensation are close to the most likely ~¢[WD.

CONCLUSIONS (1) Conditions were selected for chromatographic fraetionation of high molecular weight aliphatic polyesters in a n analytical column filled with quartz sand. (2) I t was shown that fractionation takes place not only according to molecular weights, b u t also according to end groups both in the benzene-ethyl alcohol and in the tetraehlorethane-heptane system. (3) The effect of the temperature gradient and the frequency of fractionation on the curve of molecular weight distribution was examined. (4) I t was shown that with an increase in the resolving power of fractionation in the high molecular weight region, distribution according to molecular weight gives an approximation to the most likely distribution. Translated by E. SE:~IERE

REFERENCES 1. P. J. FLORY, Principles of Polymer Chemistry, New York, 1953 2. G. J. HOWARD, Progress in High Polymers, vol. 1, London, 1961 ,3. V. I. VALUYEV, N. P. APIfKHTINA, L. V. MOZZHUKH1NA, L. P. MOSKEVIgH, Ye. P. P I S K A R E V A , R. A. SHI,YAKHTER and Ye. G. ERENBURG, Vysokomol. soyed. A9: 1871, 1967 (Translated in Polymer Sci. U.S.S.R. 9: 9, 2111, 1967)

1050

V. M. AS~:EROV e t a / .

4. V. I. VALUYEV, R. A. SHLYAKHTER, Ye. G. ERENBURG, N. P. APUKHTINA, R. P. TIGER and S. G. ENTELIS, Vysokomol. soyed. Ag: 200, 1967 (Translated in Polymer Sci. U.S.S.R. 9: 1,217, 1967) 5. V. V. YEVREINOV, V. I. GERBICH, L. I. SARYNINA and S. G. ENTELIS, Vysokomo1. soyed. A12: 829, 1970 (Translated in Polymer Sci. U.S.S.R. 12: 4, 938, 1970) 6. M. T. POPE, T. J. W E E K L Y and R. J. WILLIAMS, J. Chem. Soc., 3579, 1959 7. I. A. VAKHTINA, O. G. TARAKANOV and P. A. OKUNEV, Zh. prikl, khimii 41: 1566, 1968 8. V. V. KORSHAK, I. A. VAKHTINA, L. I. GRACHEVA and M. V. SHASHTAYEVA, Plast. massy, No. 10, 10, 1970 9. F. W. BILLMEYR and I. KATZBLAM, Macromolecules 2: 105, 1969 10. V. I. VALUYEV, R. A. SHLYAKHTER a n d N. P. APIfKHTINA, Vysokomol. soyed. B10: 147, 1968 (Not translated in Polymer Sci. U.S.S.R.) 11. H. BATZER, Makromolek. Chem. 5: 5, 1950; 1O: 13, 1953 12. W. GRICHL and H. LUCKERT, J. Polymer Sci. 30: 399, 1958 13. C. A. B A K E R and R. J. WILLIAMS, J. Chem. Soc., 2352, 1956

EQUATIONS OF MULTI-COMPONENT POLYMERIZATION DETERMINING COPOLYMERIZATION CONSTANTS*

AND

V. M. ASKEROV, 1~. M. SEIDOV a n d R . D . ABDULLAYEV All-Union Scientific Research I n s t i t u t e of Olcfins

(Received 26 July 1971) N u ~ R o u s papers have dealt with the composition of copolymers in mathematical terms [1-4]. However, the equations derived are complicated from the point of view of practical use a n d copolymerization constants are only determined approximately from experimental d a t a of b i n a r y copolymerization. This paper presents simplified equations of multi-component copolymerization which were derived using the hypothesis concerning the stationary state [2]; these enable copolymerization constants of equations of any order of multi-component copolymerization to be determined from experimental data. I t is well known t h a t rates of monomer utilization are described b y the equation -

-

d [Me]/dt = ~ ]¢~e[Mj'] [Me]

(I)

J Assuming, t h a t in the stationary state, equation

b~[Mj'][Me] =ke~[MCJ[Mj],

(2)

holds good, the corresponding proportions of monomers in the copolymer m a y be calculated from the equation derived with the solution of the simultaneous equations (1) and (2)

m,]m,=~ J

rel,c¢~,/~ r,le~,

(i, j, v~--1--n)

(3)

J

r o , = k e t / key;

rvl~=k,j / kv~

~j,=[Mj] / [M,]; ~j~=[M~]/ [Md, * Vysokomol. soyed. A15: No. 4, 932-935, 1973.

(4)

(5}