Dehydropolycondensation of thiophenol catalysed by MoCl5 and WCl6

Polymer Science U.S.S.R. Vol. 26, No. 4, pp. 953-956, 1984 Printed in Poland

0032-3950/84 $10.00+ .00 ~ 1985 Pergamon Press Ltd.

DEHYDROPOLYCONDENSATION OF THIOPHENOL CATALYSED BY MoCI5 AND WCI6* V. Z. ANNENKOVA, N. I. ANDREYEVA, V. M. ANNENKOVA, K. A. ABZAYEVA and M. G. VORONKOV lrkutsk Institute of Organic Chemistry, U.S.S.R. Academy of Sciences (Received 28 January 1983) Synthesis of polyphenylenethiols by dehydropolycondensation catalysed by MoCI~ is described and optimum conditions with a yield of 75-80 ~ and with the retention of mercapto groups in the macromolecule, established.

and WCI6

PREPARATION of polymers by dehydropolycondensation from thiophenol is of practical interest. Polyphenylenethiols, which contain free thiol groups are redox polymers and may be used as ion-exchange resins and sorbents [1]. Polycondensation of thiophenol in cold concentrated sulphuric acid [2] is well known. It results in the formation of an insoluble powdered polymer with a yield of 60~o, a unit of which in the authors opinion, has the structure of C6H3SH. The polymer softens and then breaks down at 300 ° and at higher temperature. Shortcomings of this method are the need for carrying out the process in corrosive medium, comparatively low yield and insolubility of the polymer. There is information available [3] concerning the preparation of polymers from thiophenol in glow discharge. However, no data have been quoted about polymer structure and process mechanism. A description was previously given of dehydropolycondensation of various sulphurcontaining heterocyclic monomers by the action of MoCI5 and WC16 [4-6]. We first obtained products of dehydropolycondensation of thiophenol under comparatively mild conditions by the action of MoC15 and WC16 [7]. A study was made of the effect of catalyst concentration, the duration and temperature of the process and of the solvent on the yield and properties of the product formed. The effect of the amount of catalyst and temperature was examined without solvent. Process conditions and most typical data concerning the yield and composition of polymers are tabulated. It can be seen that increasing the amount of catalyst to optimum values increases polymer yield. Temperature has a negligible effect on yield. In fact at 25 ° it only differs slightly from polymer yield at 80-100 °, other conditions being the same. At the same time increasing temperature to 120 ° slightly reduces product yield (by 8~o) and changes elemental composition. Sulphur and carbon content increases and hydrogen content in relation to the calculated content decreases, assuming that the structure of the main unit is * Vysokomol. soyed. A26: No. 4, 854-856, 1984. 953

954

V . Z . ANNENKOVA et al.

C 6 H 3 S H . A c c o r d i n g to d a t a o f e l e m e n t a l analysis, t h e p r o d u c t o b t a i n e d c o r r e s p o n d s t o t h e f o r m u l a Cs.sH2.6S. It m a y hence be a s s u m e d t h a t d e h y d r o p o l y c o n d e n s a t i o n of" t h i o p h e n o l at 120 ° results in s t r u c t u r a l changes o f t h e p r o d u c t o b t a i n e d , in which a c c o r d i n g to P M R s p e c t r o s c o p i c data, m e r c a p t o g r o u p s are o n l y f o u n d at the ends of" the m a c r o - c h a i n . I n the presence o f a solvent (heptane, CC14) the yield o f the p r o d u c t f o r m e d is muclx l o w e r (in spite o f a m a r k e d increase in the p r o p o r t i o n o f the catalyst) t h a n on c a r r y i n g o u t t h e p r o c e s s in the b u l k o f the m o n o m e r . T h e i n t r o d u c t i o n into the r e a c t i o n m i x t u r e o f t r i c h l o r o - a c e t i c a c i d ( T C A A ) which, in the a u t h o r s ' view, is a c0catalyst, does n o t increase the yield o f the p o l y m e r [8]. WCI6 catalyses d e h y d r o p o l y c o n d e n s a t i o n o f t h i o p h e n o l m o r e effectively thar~ M o C I 5 . T h e T a b l e shows t h a t w i t h a c o n c e n t r a t i o n o f t u n g s t e n h e x a c h l o r i d e h a l f t h a t o f m o l y b d e n u m p e n t a c h l o r i d e , the s a m e i n t e r m e d i a t e p r o d u c t yield is o b s e r v e d u n d e r similar c o n d i t i o n s . U s i n g WC16 (6 m o l e %) as c a t a l y s t enables m a x i m u m p r o d u c t y i e l d to be o b t a i n e d at 80 °, while the use o f M o C l s (12 m o l e ~ ) p r o d u c e s m a x i m u m p r o d u c t yield at 100 °. Thiophenol obtained by high temperature synthesis [9] was used: M----110.18; d,2° 1-0766; b.p. 168.7°; n~° 1.5893. Thiophenol was dried over calcined calcium chloride and distilled in vacuum at 28 ° (2 mmHg). A freshly distilled product was used with a degree of purity of 99.8-99.9 ~o (according to GLC) and n 2° 1-5875 and 1"5890. Dehydropolycondensation of thiophenol was carried out as follows. A catalyst sample (12 and 6 mole ~o MoCl5 and WC16, respectively) was introduced into a glass ampoule of 25 ml. The ampoule was frozen in a mixture of solid carbon dioxide and acetone and a calculated amount of monomer was then added. The ampoule was filled in a dry box in pure argon. Reaction time was 1 hr, temperature 25 to 100% After the process the reaction mass was treated with a methanol : hydrochloric acid mixture of 3 : 1 in order to remove the catalyst. The polymer formed was purified by reprecipitation from solution in DMSO using 0"5 ~o dilute solution of NaCI. M of the polymer was determined cryoscopically in dichloroethane at 20 ° by methods previously described [10 ]. Potentio metric titration was carried out in a device (pH-340) using a chloro-silver electrode and a glass electrode as standard in DMSO (20 ml), the concentration of the substance studied being 0.01 N, the titrant (C4Hg),NOH being benzomethanol (9 : 1) 0-1 N. Benzoic acid was the standard.* IR spectra of polymers (KBr pellets) were obtained using a UR-20 spectrophotometer. ESR Spectra of polymers were recorded using a THN-252 spectrometer (France). The content of gases liberated during the preparation of polymers and oligomers was determined by methods previously described [11], which are based on the absorption of chlorine and hydrogen chloride by arsenous acid and on the overall determination of chloride ion by reaction with a mercury thiocyanate compound in the presence of ferric iron. Determining hydrogen sulphide is based on its interaction with dimethyl-p-phenylenediamine and ferric chloride to form methylene blue. Dehydropolycondensation of thiophenol in the presence of MoCls and WC16, the same as for heterocyclic monomers [4-6], is accompanied by much separation of hydrogen chlolide, which points to dehydrochlorination by chlorides of the metals indicated. * Titration curves were obtained by workers of the Institute of Organic Chemistry, U.S.S.R. Academy of Sciences, T. V. Kashik and S. M. Ponomareva.

Dehydropolycondensation of thiophenol CONDITIONS

OF

DEHYDROPOLYCONDENSATION

OF

THIOPHENOL,

955 YIELD

AND

COMPOS(T1ON

OF THE POLYMER

Catalyst

Conch., mole 70

Solvent

Duration of the process,

T° I

~oC15

gdCl~

12 12 6 12 12 12 12 6 6 6

-Heptane CC14 --

I I

[ I

I

I

Found*, % Polymer Yield, 70

hr

100 25 85 80 80 100 120 80 25 80

1 2 12 12 12 1 1 1 1 12

81 76 30 60 62 80t 72 80 75 69*

C

H

65"84 64-99 63-89 64-85 64"88 65"81 67.01 65.31 66.02 65.98

3"50 3"57 3.89 3.66 3"70 3"21 2.52 3.41 3.40 3.21

S

29-0 29-35 29-45 29-16 29"30 29"05 29.02 ~ 28.99 28.80 28.91

* Calculated for (C6HaSH)N, %; C 66-70; H 3.70; S 29.60. t T h e polymer was obtained in the p r ~ e n e ~ o f triehloraeetie acid with a molar ratio o f aeld to the catalyst ranging bet weeq, 1 : 5 a n d 1 "0.5. $ Results correspond to the composition o f (C~H3S)~.

The polymers obtained were light powders, soluble in dichloroethane, T H F , formamide and D M S O with M = 2 0 0 0 - 3 0 0 0 a n d were free from metal atoms. The structure of polyphenylene thiols obtained under o p t i m u m conditions were examined by I R spectroscopy. Polymer spectra contain absorption bands of the benzene ring in the range of 1480, 1580, 1650 a n d 3070 cm -1 a n d SH bonds at 2570 cm -1 (usually a weak band). A b s o r p t i o n bands in the range of 960 to 990 c m - 1 characterize planar deformation vibration of C H of l, 2-, l, 2, 3- and 1, 2, 4-substituted benzene rings. The b a n d at 760 c m - 1 together with that at 695 c m - ~ characterizes out-of-plane deformation vibration of C H of 1, 3-substituted benzene rings, which, apparently, surround the maeromolecule. Based o n I R spectroscopic data the macromolecular fragment of polyphenylene thiol may be presented as follows:

I

SH

I

SH

According to E S R data, the concentration of paramagnetic centres in polyphenylene Ihiol was 1016 spin/g, which indicates polyconjugation of the macro-chain. The presence of thiol-groups in the polymer was also confirmed by potentiometric titration. I n acetone, or methyl alcohol polyphenylene thiol does not show acidic properties. However, the polymer solution in D M S O is a n acid and this enables S H group content to be determined. Titration curves indicate that polyphenylene thiol is a weaker SH-aeid t h a n monomeric thiophenol. This follows from semi-neutralization potentials of polyphenylene thiol ( E l = - - 6 9 5 mV) a n d thiophenol ( E t = - 5 8 0 mV). According to data of potentiometric titration, thiol group content in the polymer is 98 70 of the theoretical value. The polyphenylenethiols obtained soften at 50-55 ° a n d only begin to soften at 200-210 °. The high refractive index (n~° 1.86-1.90) is typical of these polymers.

Translated by E. S E ~

956

L . S . LITVrNOVAet aL

REFERENCES I. G. D. CASSIDY and K. A. KUHN, Okislitel'no-vosstanovitel'nyye polimery (Redox Polymers).

p. 224, Khimiya, Leningrad, 1967 2. R. P. HILD1TCH, J. Chem. Soc., 97, 2579, 1910 3. Ar. BRADLEY, Trans. Faraday Soc. 61: 4, 773, 1965 4. M. G. VORONKOV, V. Z. ANNENKOVA, N. L ANDREYEVA, V. M. ANNENKOVA and K. A. ABZAYEVA, Vysokomol. soyed. 1320: 780, 1978 (Not translated in Polymer Sci. U.S,.S.R.) :5. M. G. VORONKOV, •. Z. ANNENKOVA, N. I. ANDREYEVA, V. M. ANNENKOVA and K. A. ABZAYEVA, Vysokomol. soyed. B24: 409, 1982 (Not translated in Polymer Sci. U.S.S..R.) ~6. M. G. VORONKOV, V. Z. ANNENKOVA, N. I. ANDREYEVA, V. M. ANNENKOVA and K. A. ABZAYEVA, Izv. A N CCCP, Ser. Khim., 3, 147, 1981 7. M. G. VORONKOV, "V. Z. ANNENKOVA, N. I. ANDREYEVA, V. M. ANNENKOVA and K. A. ABZAYEVA, U.S.S.R. Pat. 698988; Byul. izobret., 43, 1979 8. M. G. VORONKOV, S. P. SUCHINSKAYA and V. B. PUKCHNAREWICH, VIII Intern. Conf. on Organometallic Chemistry, Kyoto University, Japan, 189, 1977 9. M . G . VORONKOV, E. N. DERYAGINA, L. G. KLOCHKOVA and A. C. NAKHMANO~CICH, Zh. organ, khirnii 12: 7, 1515, 1976 10. Ye. V. KUZNETSOV, S. M. DIVGUN, L. A. BUDARINA, N. I. AVVAKUMOVA and V. F. KURENKO~¢, Praktikum po khimii i fizike polimerov, 165, Khimiya, Moscow, 1977 11. Ye. A. PEREGUD, Khimieheskii analiz vozdukha, Khimiya, Leningrad, 209, 276, 1976

Polymer Science U.S.S.R. Vol. 26, No. 4, pp. 956-965, 1984 Printed in Poland

0032-3950/84 $.|0.0~+ .00 ~ /,985 Pergmmom P~ss Ltd.

M E T H O D S OF INVESTIGATION DETERMINING THE MOLAR M A S S OF POLYMERS BY THIN-LAYER CHROMATOGRAPHY BASED O N VISCOSITY CONCENTRATION EFFECTS* L. S. LITVINOVA, E. S. GANKINA an d B. G. BELEN'KI! Institute of Hetero-organic Compounds, U.S.S.R. Academy of Sciences (Received 12 July 1982) A simple method was proposed for determining M of polymers based on concentration dependences of viscosity in thin-layer chromatography. A universal dependence on intrinsic viscosity [t/] was derived for various classes of polymer of the length of the chromatographic zone of the polymer during its motion with the eluent front for a fixed amount of polymer. The method developed by the authors enables [q] to be determined using any type of characterized polymer as calibration reference samples. The error of determination of [rt] is ~ 10 ~ . * Vysokomol soyed. A26: No. 4, 857-864, 1984.