Macromolecular properties of statistical chloroprene-dichlorobutadiene copolymers in dilute solutions

1218

A. V. GEVORKYA_~et al.

9. 10. 11. 12.

V. V. MAZUREK a n d O. P. BUDANOVA, Chem. High Polymers 24: 91, 1967 C. BEERMAN a n d A. BESTIAN, Angew. Chemie 71: 618, 1959 F. S. D'YACHKOVSKH and A. Ye. SHILOV, Zh. tim. khim. 41: 2515, 1967 F. S. D'YACHKOVSKII, A. Ye. SHILOV and N. Ye. KHRUSHCH, Kinetika i kataliz 8: 1230, 1967 13. F. S. D'YACHKOVSKII, A. Ye. SHILOV a n d N. Ye. KHRUSHCH, Kinetika i kataliz 9: 1006, 1968

MACROMOLECULAR PROPERTIES OF STATISTICAL CHLOROPRENE-DICHLOROBUTADIENE COPOLYMERS IN DILUTE SOLUTIONS* A. V. GEVORKYAtq, YE. S. YEGIYAIq, N . G. 0GA~CESYA~¢

and R. V. BAGDASARYA~ All-Union Polymer Research and Development Institute (Received 15 April 1969)

EARLIER studies had examined the conformational properties of chloropren~ isoprene macromolecules in solution [1]; these were based on the measurement of the intrinsic viscosity of fraction solutions away from the 0-point. Investigations directly in the 0-state would give more accurate information about the specific features of the hydrodynamic behaviour of copolymer macromolecules in dilute solutions. The above was the aim of the work reported here; it describes the results of light scattering studies and of solution viscosity measurements on fractions of a statistical ehloroprene-dichlorobutadiene (CPDCB) copolymer. EXPERIMENTAL The original eopolymer sample is known as a technically valuable elastomer. I t s trade name is Nairit NG; it was produced b y emulsion polymerization at 20°C a n d the initiator was potassium persulphate, the chain-branching regulator tertiary dodecyl mercaptan. The derivations of the relative comonomer activities which determine the chain structure in the case of the emulsion copolymerization, slightly differed from u n i t y [2], so that statistical copolymer formation could be assumed [3]. The copolymer composition (XA=0"6) was determined b y elemental analysis (this result was also confirmed b y the infrared spectroscopy results and b y rcfractometry). The copolymer was purified b y repeated extraction with acetone vapour and reprecipitation from penzene solution with methanol. The purified eopolymer (3/Iw=4.36x 105) was fraction* Vysokomol. soyed. A12: No. 5, 1078-1081, 1970.

Macromolecular properties of chloroprene-dichlorobutadiene copolymers

1219

p r e c i p i t a t e d i n t o 15 f r a c t i o n s f r o m a 1 % b e n z e n e s o l u t i o n w i t h m e t h a n o l a t 20°C. T h e first 4 f r a c t i o n s w e r e d i s c a r d e d b e c a u s e o f t h e large gQl c o n t e n t . T h e m o l e c u l a r w e i g h t s (mol.wt.) o f t h e f r a c t i o n s w e r e d e t e r m i n e d f r o m light s c a t t e r i n g m e a s u r e m e n t s in c a r b o n t e t r a c h l o r i d e . T h e intrinsic viscosities o f t h e solutions w e r e d e t e r m i n e d in a m o d i f i e d U b b e l o h d e t y p e v i s c o m e t e r ( h a n g i n g level) w i t h a CCI~ flow t i m e v ~ 100 sec. N o c o r r e c t i o n s w e r e m a d e for t h e k i n e t i c e n e r g y a n d t h e g r a d i e n t f u n c t i o n [4]. T h e purificat i o n a n d p r e p a r a t i o n o f t h e solutions u s e d in t h e s e t e s t s w a s t h a t d e s c r i b e d earlier [5].

RESULTS

The similar refraction increments of the copolymer and the respective homopolymers in CC14 (vAB----0"102, VA=0"104, VB=0"100 ) formed the basis for the assumption that errors due to compositional non-uniformity are small [6]. The results of fractionations [7], and those of the unit content per chain obtained on a series of fractions confirmed the insensitivity of the selected solvent-precipitant system to the copolymer composition [8]. The intrinsic viscosities of the CPDCB fraction solutions were measured in CC14 (at 20°C) and in a 0-solvent. The 0-temperatures (4.7 : 1 w/w benzene +methanol, 38.5°C) were determined from the critical polymer-solvent mixing temperatures (Tcrit)-mol. wt. function [9]:

(°)

Tcri~=O 1 - - ~ - i 7 ~ " RESULTS

OF THE LIGHT-SCATTERING

AI~D VISCOSITY

(1)

MEASUREMENTS

O1W

CPDCB

FRACTIOI~

SOLUTIONS

Fraction No.

V VI VII VIII IX X XI XlI * XlII XIV XV

[t/], d l / g

(~2)L h

Mw × 10 ~

6'25 5"27 4"55 2"50 2"20 1"82 1"23 0"89 0"76 0"48 0"29

CC14

0-solvent

1.75 1.50 1.30 0.90 0.80 0-68 0.52 0.40 0.35 0.24 --

0-80 0.70 0.61 0.49 0.43 0-41 0.38 O.24 0-21 0.19 0-18

559 510 460 353 322 297 254 196 177 147 123

(~)~, 451 418 384 291 267 244 204 169 155 125 96

1.24 1-22 1.20 1'21 1"20 1'22 1"24 1.16 1.32 1.18 1'28

* The mol.wt, from fraction XII onwards were determined in accordance with functions (2) and (3) found by us.

The molecular characteristics of the CPDCB found from the light scattering measurements and the viscosities of the fraction solutions are contained in the Table.

1220

A. V. GEVORKYAN e$ at.

The intrinsic viscosity [7] of the CPDCB fraction solutions are shown as a function of -~/w (double logarithmic scale) in Fig. 1, described b y the following function: [7]---- 0.6x 10 -~ ]~/o.77 (in CC1) (2) [~]0----10.6 x 10 -~ ~l)°w5° (in 0-solvent).

(3)

Equation (3) shows that a Gaussian molecular coil structure is retained in the 0-solvent, which is typical of the homopolymer macromolecules in solutions. The "unperturbed dimensions" of the CPDCB macromolecules were evaluated on the basis of the known Flory equation [9]: M

•

(4)

The ¢0-values were taken to be 2.86 × 1021 mole -1 [10]. The Ke-value (or the skeletal dimensions, since Ko~--~o(h~o/M) '1~) were also assessed b y extrapolation, using non-ideal solvents, as proposed for homopolymers [11] (see Fig. 2, curve a)

(5)

[t/]- M-11*-~ Ko +0.51q~oBM 1/, .

tog 2"0 r-

/

9.1o

lOgMw I'0

,i

a

I

0

FIG, 1

0.5-

1.0 MwI/'2 , I0 -a

FIG. 2

FIG. 1. log [t]] as a function of log/1Iw for CPDCB fraction solutions in CCI, (1) and a 0-solvent (2). FIG. 2. [~].M~ as a function of/1I*w for CPDCB fraction solutions in: a--CC14, b--0-solvent. The Ke-value .(1 × 10 -8) for CPDCB agrees well with the experimental value determined directly at the 0-point, as Fig. 2 shows. The experimental characteristics at the 0-point are also illustrated b y the preservation of the condition B----0 in the polymer-solvent reaction in the "unperturbed" state (Fig. 2, curve b). The theoretical macromolecular dimension (~2)~/,, applicable to a free rotation model, was calculated from formula [12]:

/EA.

(6)

This is based on the theory that a radical mechanism of production of polymer molecules at normal polymerization temperatures will give rise to a predominance of the 1,4-trans configuration [13]. The results of these calculations, and also the

Maeromolecular properties of chloroprene-dichlorobutadiene eopolymers a = ~

1221

ratios are listed in the Table. The slightly too low a-value, compared

with that of homopolymers of the diene series and of polychloroprene molecules, is attributed to the fact t h a t the unperturbed dimensions of the PCDCB molecules had been obtained on the basis of hydrodynamic properties (the intrinsic viscosity of the fraction solutions in this case). The contour length (i.e. the length of a fully extended chain without valence angle deformation) of macromolecules L is known to be: L = N A = loZ = l o ( M / M o ) ,

(7)

in which l0 and Me are the length and the mass of the monomer unit respectively, Z is the degree of polymerization (/o= 5 J~ was accepted for the CPDCB molecules). As to the Gaussian chains (where the number of statistical segments N>>I), (8)

h2=NA~.

The combination of eqn. (7) with (8) for CPDCB macromolecules (average of all fractions) gave the number of monomer units, S = 2, for one statistical segment. The results given above indicate that any additional near-order reactions occurring in molecular chains of the eopolymer will not affect the conformational properties (or unperturbe6 dimensions) of the PCDCB maeromolecules. CONCLUSIONS

(1) The light-scattering and viscosity of the fraction solutions of a statistical ehloroprene-diehlorobutadiene copolymer (X~=0.6) in CC14 and in 0-solvent (4.7:1 benzene+methanol, 38.5°C) was investigated. (2) The functions'associating the intrinsic viscosity of the fraction solutions with mol. wt. ~r w were established to be: [7]=0.6× 10-' ~0~77 (in CO1,) [~/]0= 10.6 × 10 -4 _~/0js0 (in a 0-solvent) . (3) The findings give reason to believe t h a t any additional near-order reactions in the molecular chains of the copolymer will not affect the "unperturbed dimensions" of the eopolymer macromolecules. Translated by K. A. ALLEN REFERENCES 1. A. V. GEVORKYAN, Ye. S. YEGIYAN, R. A. KARAPETYAN and L. G. MELKONYAN,

Ueh. zapiski Yerevan gos. univ., No. 3, 40, 1969 2. N. G. KARAPETYAN, I. S. BOSHNYAKOV and A. S. MARGARYAN, Vysokomol. soyed. 7: 1993, 1965 (Translated in Polymer Sei. U.S.S.R. 7: 11, 2185, 1965) 3. T. ALFREY, J. BORER and G. MARK, Copolymerization, Izd. inostr, lit., 1963

1222

M. V. TSILIPOTKIlVAeta/.

4. A. V. GEVORKYAN, Armyan. khim. zh. 19: 245, 1966 5. A. V. GEVORKYAN, R. V. BAGDASARYAN and L. G. MELKONYAN, Izd. Akad. Nauk Armyan. SSR, Fizika 1: 75, 1966 6. H. BENOIT, Ber. Bunsenges. Physik. Chem. 70: 286, 1966 7. A. V. GEVORKYAN, R. V. BAGDASARYAN, Ye. S. YEG1YAN and N. G. OGANESYAN, Nauch. trudy Vsesoyuz. nauch.-issled, inst. polimerov, issue 1-2, 1970 8. A. D. LITMANOVICH and A. V. TOPCHIEV, Neftekhimiya 3: 335, 1963; A. D. LITMANOVICH and V. Ya. SHTERN, Dokl. Akad. Nauk SSSR 147: 1389, 1963 9. P. FLORY, Principles of Polymer Chemistry, N. Y., 1953 10. O. B. PTITSYN and Yu. Ye. EIZNER, Vysokomol. soyed. 1: 966, 1959 (Translated in Polymer Sci. U.S.S.R. 1: 3, 351, 1960) 11. W. STOCKMAYER and M. FIXMAN, J. Polymer Sci. CI: 137, 1963 12. H. MARKOVITZ, J. Chem. Phys. 20: 868, 1952 13. I. MAYNARD and W. MOCHEL, J. Polymer Sci. 13: 251, 1954 14. I. Ya. PODDUBNYI, Ye. G~ ERENBURG and M. A. YEREMINA, Vysokomol. soyed. A1O: 1381, 1968 (Translated in Polymer Sci. U.S.S.R. 10: 6, 1603, 1968) 15. A. V. GEVORKYAN, Izd. Akad. Nauk Armyan. SSR, Fizika 1: 195, 1966

EFFECT OF THE TYPE OF SOLVENT AND PRECIPITANT AND THE METHOD OF FILM PREPARATION ON THE PORE STRUCTURE OF POLYMERS* M. V. TSILIPOTKINA, A. A. TAGER, E. B. MAKOVSKAYA a n d V. PARTINA A. M. Gor'kii State University of the Ural

(Received 15 April 1969) WORK in recent years has revealed that the structure and the mechanical properties of polymers depend on the type of solvent used to produce them [1, 2]. The changes in the mechanical strength and useful life of films produced from such polymers can be associated with diverse conformational changes of the macromolecules due to the particular solvent, changes in the dimensions and shape of the macromolecular structures, and also to differences in packing d e n s i t y (microporosity). T h e l a t t e r p a r a m e t e r d e t e r m i n e s t h e m e c h a n i c a l , dielectric a n d o p t i c a l p r o p e r t i e s o f such m a t e r i a l s , its p e r m e a b i l i t y b y gases, r e a g e n t s a n d dyes, i o n - e x c h a n g i n g p r o p e r t i e s , t h e k i n e t i c p a r a m e t e r s o f ion e x c h a n g e , etc. W e h a v e b e e n u n a b l e to find a n y s y s t e m a t i c studies dealing w i t h t h e effect o f t h e s o l v e n t t y p e on t h e p o r e s t r u c t u r e o f t h e p o l y m e r . * Vysokomol. soyed. A12: No.5, 1082--1090, 1970.