Three-dimensional polycondensation of trifunctional estero-acids with glycols

T H R E E - D I M E N S I O N A L POLYCONDENSATION OF TRIFUNCTIONAL ESTERO-ACIDS W I T H GLYCOLS* K. A. ANDRIANOV, M. B. FROMBERG and T. M. BELKINA V. I. Lenin All-Union Electro-Technlcal Institute (Received 28 June 1966)

A DESCRIPTION has previously been given [1-3] of the synthesis of network polyesters with an ordered molecular structure by the method of reacting oligomerie estero-acids with glycols and organosilieon alcohols. In these, a study was made of the three-dimensional polycondensation reaction and certain rules in this reaction were brought to light, using as examples the reaction between glycols and pentaerythritol tetraadipate, and the reaction between other tetrafunctional estero-acids and tri- and tetrahydric organosilicon alcohols. The three-dimensional polycondensation reaction between various trifunctional estero-aeids and glycols has been investigated in the present work. I t was thus of interest to find out if the rules found for the three-dimensional polycondensation of tetrafunctional estero-aeids with glycols and other compounds m a y be extended to the polycondensation process with trifunctional estero-acids. The trisuccinate, triadipate and trisebacate of trimethylolpropane were used as the estero-acids [4]. The reaction was carried out according to the equation C~H~C[CH2OCO(CHs)nCOOH]8 -~ 1,5HO(CHs)mOH .-H2o

I

I

-->C2Hs--C--CH~OCO(CH2)nOCO(CH2)= OCO(CH2)nOCO--CH~--C--C2Hs, where n = 2 , 4, 8 m = 2 , 4. Such polymers have a regular alternation of the structural units, since the distance between the atoms forming the network points is constant; it depends on the distance between the hydroxyl groups of the glycol and the number n (the branch length) in the estero-aeid. As experiments have shown, the reaction rate depends substantially on the branch length in the estero-acid. It has been established that the duration of the reaction up to the moment of gel-formation rises with an increase in the number n of the estero-acid (Fig. 1). A similar relationship is observed when the acid and ester numbers are changed (Fig. 2), and also when the specific viscosity of the polycondensation products from the estero-acids and glycols is changed (Fig. 3). * gysokornol, soyed. A9: No. 10, 2254-2258, 196'/. 2550

Polycondensation of trifunctional estro-acids with glycols

2551

T h e r e a c t i o n b e t w e e n t r i f u n c t i o n a l e s t e r o - a c i d s a n d g l y c o l s is o f t h e s e c o n d o r d e r (Fig. 4a) since, i n all cases, a l i n e a r r e l a t i o n s h i p b e t w e e n t h e r e c i p r o c a l o f t h e c a r b o x y l g r o u p c o n c e n t r a t i o n a n d t h e r e a c t i o n t i m e is o b s e r v e d . The reaction rate constants for the reaction between estero-acids and glycols A 12 8 ¢ 0 I

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FIe. l. Relationship between the duration of polycondensation between estero-acids and glycols up to the moment of gel-formation, and the number of methylene groups in the estero-acid: 1--polyeondensation with ethyleneglycol; 2--with butyleneglycol. A is the duration of the reaction up to the moment of gel-formation, in hours; B is the number of methylene groups in the estero-acid. rng KOH/,q +400

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FIQ. 2 FIG. 3 FIG. 2. Change in the (a) the acid, and (b) the ester numbers during polycondensation between estero-acids and glycols. 1, 1'; 2, 2' and 3, 3' refer respectively to the trisuecinate, triadipate and trisebacate of trimethylolpropane: 1, 2, 3--polycondensation with ethylene glycol; 1', 2', 3' -- polycondensation with butyleneglycol. FIG. 3. Relationship between the specific viscosity and the duration of the reaction between estero-acids and glycols. 1, 1'; 2, 2" and 3, 3" refer respectively to the trisuccinate, triadipate and trisebacate of trimethylolpropane: 1, 2, 3--polycondensation with ethyleneglycol; 1', 2', 3'--polycondensation with butyleneglycol.

2552

K.A. A~D~ov

et ed.

were calculated from the equation for a second order reaction [5] k=P/t.cAO. •( l - - P ) , where P is the degree of completion of the reaction at moment t, cx °is the initial carboxyl group concentration (Table 1). T A B L E 1. R A T E CONSTANTS Il~ T H E POLYCONDENSATION REACTION B E T W E E N ESTERO-ACIDS AND GLYCOLS AT 1 5 0 ° C

Estero-acid

Trisuceinate of trimethylolpropane Triadipate of trimethylolpropane Trisebacate of trimethylolpropane

Reaction rate constant, /c × 10s (mg-equiv./g)-lmin -1 ethyleneglycol 1,4-butyleneglyeol 3.13 0"84 0-53

3"11 0"81 0'50

The values of the reaction rate constants obtained also give evidence of the fact that, in the reaction between estero-acids and glycols, the reaction rate falls with an increase in the branch length of the estero-acid. The degree of completion of the reaction as a function of the polycondensation time is shown in Fig. 5, from which it m a y be seen that the maximum value of this quantity is reached most rapidly in the reaction between trimethylolpropane trisuecinate and glycols, and most slowly of all in the reaction of trimethylolpropane trisebacate. As m a y be seen, the degree of completion of the reaction at the instant of gel-formation is 62-67%; this is less than the values calculated from Flory's equation [6], according to which, for the present case,

.P~-----acr=l/(f--1),

and hence -P----~/~-'5=0.71.

The degree of completion of the polycondensation reaction between glycols and trifunctional estero-acids differs considerably less from the values calculated b y means of Flory's equation than do those calculated for the case of the polycondensation of tetrafunetional estero-acids. Thus the degree of completion of the reaction does not depend on the branch length in the estero-acid; this m a y be clearly explained in the following way. With an increase in the distance between the carboxyl, groups in the estero-acid, the mobility of the maeromolecular chain increase, the functional groups being contained at the ends of the branches; this lez~s to a large possibility of interchain interaction, and as a consequence to a smaller degree of completion of the reaction at the instant of gelformation [2,4]. On the other hand, a more open polymer Structure is formed with an increase in the branch length in the estero-ecid, and such a polymer will have better solubility and it will be more difficult to separate the gel-fraction. This, in its turn, will lead to an increase in the degree of completion of the reaction at the moment of gel-formation [2). I t is probable that in the polycondensation of trifunctional estero-acids with glycols, the mutual effect of these factors leads to the fact that the degree of completion of the reaction does not depend on the branch length in the estero-acid.

Polycondensation o f trifunctional estro,acids w i t h glycols

2553

In the polycondensation of trifunctional estero-acids, as distinct from tetrafunctional estero-acids, with glycols, less branched polyesters are obtained, and the effect of the first factor, which reduces the degree of completion of the reaction 0"8 - l i e

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FIQ. 4. Relationship between the duration of polycondensation between estero-acids and glycols, and (a) the reciprocal of the earboxyl group concentration, and (b) the reciprocal of the soluble fraction concentration. 1, 1'; 2, 2' and 3, 3' refer respectively to the trisuecinate, triadipate and trisebacate of trimethylolpropane: 1, 2, 3--polyc0ndensation with ethyleneglycol; 1% 2% 3'--polycondensation with butyleneglycol. FIG. 5. Degree of conversion up to the m o m e n t of gel-formation as a function of the duration of the reaction between estero-aeids and glycols. 1, 1', 2, 2" and 3, 3' refer respectively to the trisuccinate, triadipate and trisebaeate of trimethylolpropane: 1, 2, 3--polycondensation with butyleneglycol.

of th• oligomers as compared with the monomers, is of less importance. This evidently provides an explanation of the fact that the degree of completion of the polycondensation reaction with trifunctional estero-acids differs less, as compared with tetrafunctional estero-acids, from the values calculated according to Flory's equation. The kinetics of the polycondensation of trifunctional estero-acids with glycols after gel-formation are shown in Fig. 4b, in the form of the relationship between

2554

K.A.

ANDRIANOV et a~.

t h e reaction t i m e a n d values of the reciprocal of t h e c o n c e n t r a t i o n o f t h e soluble p o l y m e r fraction. As m a y be seen f r o m this Figure, t h e p o l y c o n d e n s a t i o n o f trif u n c t i o n a l estero-acids with glycols proceeds a f t e r gel-formation as a second order reaction. T h e reaction r a t e constants are p r e s e n d e d in T a b l e 2. T A B L E 2. R A T E CONSTANTS I N T H E POLYCONDENSATION R E A C T I O N B E T W E E N ESTERO-ACIDS AND GLYCOLS A F T E R GEL-FORMATION AT

150°C

Reaction rate constant, k* × 108 (arbitrary unit) -1 (min -1)

Estero-acid

ethylcneglyeol

1,4-butyleneglycol

32"8 6"44

31.1 5.77

2"78

- 2.26

Trisuccinate of trimethylolpropane Triadipate of trimethylolpropane Trisebacate of trimethylolpropane

* k=P/[t.v] (l--P)], where P is the gel-fraction yield; t--time; and e ~ = l - - s o l u b l e fraction content before the moment of gel-formation.

T h e d a t a in Table 2 indicate t h a t t h e r a t e of t h e p o l y c o n d e n s a t i o n reaction between trffunctional estero-acids a n d glycols after gel-formation also depends on the b r a n c h length in t h e estero-acid, a n d becomes less with an increase in b r a n c h length. A f t e r t h e p o i n t o f gel-formation, t h e soluble f r a c t i o n of t h e polyesters falls, b u t the acid n u m b e r of the soluble f r a c t i o n changes v e r y little Table 3). This is in a g r e e m e n t with d a t a o b t a i n e d previously [2]. T A B L E 3. A C I D NUMBERS OF T K E PRODUCTS OF T H E POLYCONDENSATION R E A C T I O N B E T W E E N ESTERO-ACIDS AND GLYCOLS A F T E R G E L - F O R ~ T I O N

Reaction time after gel-formation, hr

Starting materials estero-acid Trisuccinate of trimethylolpropane Trisuceinate of trimethylolpropane Triadipate of trimethylolpropane Triadipate of trimethylol. propane Trisebacate of trimethylolpropane Trisebacate of trimethylolpropane

glycol

0

3

9

15

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110.2

109"9

112"0

95.5

92-8

92.0

95.9

103-0

107.4

110.2

103-7

1,4-Butyleneglycol

89.5

91.2

89-3

92.0

Ethyleneglyeol

70.4

71.8

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74.2

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71-5

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72.0

Ethyleneglycol l'4-Butyleneglycol Ethyleneglycol

EXPERIMENTAL

The following compounds were used in this work: ethyleneglycol with a boiling point of 196-197°C, n~ 1.4321; 1,4-butyleneglycol with a boiling point of 234-235°C, n~ 1.4451;

Polymers based on halogeno-anil acids

2555

trimethylolpropano trisuccinate, acid number 387 (calculated, 386-7); trimothylolpropane triadipate, acid number 322 (calculated, 324); trimethylolpropane trisebacate, acid ntunbor 242 (calculated, 244.9). The estero-acids were obtained by the method described previously [4]. Polycondensation of e~tero-acids with glycols. The estero-acid and glycol were placed in a three-necked flask, equipped with a thermometer, stirrer, condenser, stopper and tube for supplying nitrogen, and were heated in a current of nitrogen at 150°C. At fixed intervals of time, samples were removed to determine the acid and ester numbers and the specific viscosity of 10% solutions of the polyester in ethylcelluloso. The point of gel-formation was determined as the moment when the reaction products ceased to dissolve in boiling acetone. After the gel-formation point, the reaction was carried out in the same conditions without stirring. Samples were taken periodically, and in these the soluble fraction was determined by extraction with acetone in a Soxhlet apparatus. The gel-fraction was dried to constant weight at 50-60°C and at a residual pressure of 10-12 mmHg. The acid number was determined for the soluble fraction. CONCLUSIONS (1) T h e p o l y c o n d e n s a t i o n r e a c t i o n b e t w e e n t r i f u n c t i o n a l e s t e r o - a c i d s a n d glycols h a s b e e n s t u d i e d . I t h a s b e e n s h o w n t h a t t h e r e a c t i o n b e t w e e n e s t e r o acids a n d glycols is o f t h e first order. (2) T h e r a t e o f r e a c t i o n b e t w e e n e s t e r o - a c i d s a n d g l y c o l s increases w i t h a d e c r e a s e in t h e d i s t a n c e b e t w e e n t h e c a r b o x y l g r o u p s o f t h e estero-acid.

Translated by G. F. MODLEN REFERENCES 1. K. A. ANDRIANOV and V. N. YEMEL'YANOV, Izv. Akad. Nauk SSSR. Otd. khim. n. 1267, 1963 2. K. A. ANDRIANOV and V. N. YEMEL'YANOV, Plast. massy, No. 2, 22, 1965 3. K. A. ANDRIANOV and V. N. YEMEL'YANOV, Vysokomol. soyed. 4: 668, 1966 (Not Translated in Poly. Sci. U.S.S.R.) 4. K. A. ANDRIANOV, M. B. FROMBERG and T. M. BELI(INA, Vysokomol. soyed. 7: 1456, 1965 (Translated in Poly. Sci. U.S.S.R. 7, 8, 1613, 1965). 5. P. FLORY, J. Amer. Chem. Soc. 61: 3334, 1939 6. P. FLORY, J. Amer. Chem. Soc. 63: 3089, 1941

POLYMERS BASED ON HALOGENO-ANIL ACIDS* A. A. GUROV, B. I. LIOGO•'KII a n d A. A. BERLr~ Institute of Chemical Physics, U.S.S.R. Academy of Sciences

(Received 3 De~ember 1966) POLYMERS c o n t a i n i n g q u i n o n e w i t h a s y s t e m o f ~ , ~ - c o n j u g a t e d b o n d s a r e h e a t a n d r a d i a t i o n - r e s i s t a n t e l e c t r o n - e x c h a n g e a g e n t s a n d , in a d d i t i o n , h a v e p a r a m a g n e t i c , s e m i - c o n d u c t o r a n d c a t a l y t i c p r o p e r t i e s [1]. I n a p r e v i o u s p a p e r [2] * Vysokomol. soyed. A9. No 10, 2259-2266, 1967.