- Email: [email protected]
Synthesis and properties of some polycyanurates
Fur. Polym. J. Vol. 25, No. 2, pp. 193-195, 1989 Printed in Great Britain. All rights reserved
0014-3057/89 $3.00+0.00 Copyright © 1989 Pergamon Press plc
SYNTHESIS A N D PROPERTIES OF SOME POLYCYANURATES R. B. NAIK* and P. P. SHAH Department of Chemistry, South Gujarat University, Surat-395 007, Gujarat, India (Received 14 April 1988)
Abstract--Six polycyanurates were synthesized by stirred interfacial polycondensation of 2-diphenylamino-4,6-dichloro-s-triazine with each of the aromatic diols, bisphenol-A: bisphenol-C; bisphenol-S; phenolphthalein; 1,5- and 1,7-dihydroxynaphthalene. The polycyanurates, obtained in 60-80% yield, possessed reduced viscosities in the range 0.1~3.19 dl/g and were soluble in chlorinated solvents such as chloroform, dichloroethane and methylene chloride. The polycyanurates were characterized by i.r. spectra. The density and thermal stability of each of the polycyanurates were also determined. Polycyanurates derived from bisphenol-A and bisphenol-C were found to possess greater thermal stability than the others.
INTRODUCTION Polycyanurates derived from 2-R-4,6-dichloro-striazine and aromatic diols have gained importance in the field of thermally stable polymers. Earlier attempts [I-4] based on high temperature solution polycondensation led to formation of low molecular weight, insoluble and infusible polycyanurates. The stirred interracial polycondensation technique has been reported to yield high molecular weight polycyanurates [5-11]. Polycyanurates are noted for high transition temperatures and thermal stabilities. In the present investigation, polycyanurates synthesized by interracial polycondensation of 2-diphenylamino-4,6-dichloro-s-triazine (DPADCT) with each of several aromatic diols viz. bisphenol-A (BPA), bisphenol-C (BPC), bisphenol-S (BPS), phenolphthalein (Ph), 1,5- and 1,7-dihydroxynaphthalene (DN-1,5 and DN-1,7) are reported. The polycyanurates have been characterized by viscosity, solubility, density, i.r. spectroscopy and thermogravimetry.
aqueous solution and the emulsion was stirred vigorously for 5 hr at 25°. The organic layer containing the polymer was isolated and washed with water; polymer was precipitated from methanol. It was filtered, washed with water, methanol, and finally with acetone. The yield of the dried polymer was 78%. The polymer was further purified by dissolving in chloroform followed by reprecipitation from petroleum ether. A solution of the polymer in chloroform (1 g/dl) had a reduced viscosity of 0.19 at 30°. Other polycyanurates (see Table I), were prepared by this procedure. Characterization methods Reduced viscosities of polycyanurates were determined for 1 g/dl solutions in chloroform at 30° using an Ubbelohde suspended level viscometer. The densities of polycyanurates were determined using suspension method [14]. The liquid system used was carbon tetrachloride and petroleum ether. i.r. Spectra of the polycyanurates were recorded on a Perkin-Elmer i.r. spectrophotometer using a KBr pellet technique. Thermogravimetric analyses (TGA) of the polycyanurates were performed using a Mettler TA 3000 system at a heating rate of 10°/min in air.
RESULTS AND DISCUSSION
EXPERIMENTAL Materials DPADCT was synthesized by the reported method [12] and purified by crystallization from ethanol (m.p. 172°). BPA was crystallized from benzene (m.p. 156~). BPC [10] and BPS [13] were synthesized by published methods and were crystallized from benzene (m.p. 187 and 239° for BPC and BPS, respectively). Commercially available phenolphthalein (BDH), DN-I,5 and DN-1,7 (Sisco Lab) were purified by crystallization. Benzyl dimethyl hexadecylammonium chloride (BDMHDACI) (BDH) was used as received. AR grade solvents were used. Synthesis of polycyanurates A typical example of interfacial polycondensation is given below for the formation of polycyanurate of BPA. A solution of BPA (2.28g, 0.01 moll NaOH (0.8g 0.02mol) and BDMHDACI (0.125g) in distilled water (50 ml) was stirred at 25~. A solution of DPADCT (2.17 g, 0.01 mol) in chloroform (25 ml) was rapidly added to the
*To whom correspondence should be addressed.
Several characteristics of polycyanurates are now reported (Table 1). The interface system used a good solvent (chloroform). Polycyanurate formation was found to be possible only with the use of cationic emulsifier. Both surfactant and catalytic functions could be combined through the use of cationic surfactants which, as quaternary a m m o n i u m compounds, could aid in transfer of monomer between phases [15]. Cation emulsifiers have been exclusively used for the synthesis of polycyanurates [5, 8-11]. Examination of reduced viscosity values reveals that, among chloroform soluble polycyanurates, PCBPA has the highest whereas PCBPS has the lowest solution viscosity. The trend of these values reflect order of relative reactivity of bisphenols. BPA is the least acidic and hence most reactive towards nucleophilic displacement reaction and hence leads to the formation of polycyanurate of a comparatively higher molecular weight. Due to electronic effects BPS is highly acidic and hence least reactive and 193
R. B. NAIK and P. P. SHAH
194
Table 1. Characteristics of polycyanuratesderived from DPADCT Polymer Yield ~lsp/C= Aromatic code (%) (ml/g) d (g/cm3) dial 75 19.0 1.218 Bisphenol-A PCBPA 75 17.0 1.202 BisphenoI-C PCBPC 60 5.0 1.327 BisphenoI-S PCBPS 67 7.0 1.278 Phenolphthalein PCPh 65 18.0b 1.254 1,5-Dihydroxynaphthalene PCDN-1,5 65 16.0b 1.278 1,7-Dihydroxynaphthalene PCDN-1,7 ~Chloroform, 30% bN,N'-dimethylformamide,30°. leads to lower molecular weight polycyanurate. Of the two isomeric dihydroxy naphthalenes, the 1,5isomer seems to be more reactive probably because of its greater symmetry.
Densities of polycyanurates Densities of polycyanurates determined at 25 ° by suspending each of the polycyanurates in a mixture of carbon tetrachloride and petroleum ether and subsequently measuring the density of the liquid mixture by a pyknometer are also presented in Table 1. Densities, calculated theoretically on the basis of the structural concept proposed by Slonimskii et al. [15] are also presented; an average value of 0.684 for packing coefficient, k, was used for this calculation; k was approximated from the slope of a line best fitting the
d (calc.) (g/cm3) 1.200 1.197 1.315 1.268 1.256 1.256
liii . . 4
:"l
;6o
F
d - M /NA ~ AV, i
curve [15]. Volume increments, Al/i, of relevant atomic groups making up the polycyanurate repeat unit have been calculated by us and used by calculate intrinsic volume. Comparison of experimental and calculated densities shows a good correlation.
AI/i (A3) 446.6 485.6 426.5 503.2 365.4 365.4
0
f
3
100 zoo 300
400
500
6oo
,
700
Temperature ("C] Fig. 1. TGA thermograms at a heating rate of 10°/min in air (1) PCBPA, (2) PCBPC, (3) PCBPS, (4) PCPh, (5) PCDN-1,5 and (6) PCDN-1,7.
i.r. Spectral characteristics The i.r. spectra of these polycyanurates exhibited the following c o m m o n characteristic absorption frequencies (cm -~) at 815-830 and 1670-1430 attributable to out-of-plane and in-plane vibrations of s-triazine ring, respectively, at 1300-1240 attributed to vibrations involving aryl-ether linkage [16-18]. In addition, the spectra exhibited a few absorption frequencies based on which these polycyanurates can be distinguished from one another. These frequencies (cm-~ ) are: 420, 550 ( C - - C deformation vibrations of propyl link), 1180 ( C - - C skeletal vibrations of propyl link), 1375 and 1385 (both of nearly equal intensity due to C - - C H 3 deformations of propyl group) for PCBPA; 535, 940, 980 (all C---C deformation vibrations of cyclohexane ring) for PCBPC: 570, 590
(scissoring vibrations of sulphone group), 1160 and 1370 (symmetric and assymetric stretching vibrations of sulphone group) for PCBPS; 780, 1085 (odisubstituted phenyl ring), 1775 ( C - - O stretching of lactone group) for PCPh. Spectral distinction between PCDN-1,5 and PCDN-1,7 which may be based on frequencies in the region 1650-1600 and 1630-1575 where ring stretching vibrations of substituted naphthalenes appear, was found to be difficult since these regions were heavily crowded by ring stretching vibrations of phenyl rings.
Thermal characteristics of polycyanurates T G A thermograms of polycyanurates are shonw in Fig. 1. Several temperature characteristics such as To
Table 2. Temperature CC) characteristics of polycyanurates Residue Polymer TO T,0 Step-I Step-ll Step-Ill T, IPDT at 700" PCBPA 350 415 425 605 -510 602 3.0 PCBPC 360 405 420 525 -470 552 11.0 PCPh 230 290 280 360 545 440 515 17.0 PCBPS 290 360 370 535 -505 510 40.0 PCDN-I,5 100 145 160 440 -195 330 35.0 PCDN-1,7 100 145 180 --185 305 18.0 T0--initial decomposition temperature; T)0--temperaturefor 10% wt loss; Tm.,--temperature for maximum rate of decomposition; T,--temperature for half volatilization;IPDT--integral procedural decompositiontemperature.
Polycyanurates--synthesis and properties (initial decomposition temperature), 7"10(temperature for 10% wt loss), Tmax (temperature for maximum rate of decomposition) and Ts (half-volatilization point temperature), which may be used for qualitative assessment of relative thermal stabilities of polycyanurates, are presented in Table 2. With dynamic heating, To and Tl0 are some of the main criteria for thermal stability of polymers. The higher the values of To and T~0, the greater the heat stability of a given polymer [19]. Comparison of T o and/or T~o for polycyanurates indicates that the thermal stabilities of PCBPA and PCBPC are quite similar and that PCBPS, PCPh, P C D N - I , 5 and P C D N - I , 7 follow the former in decreasing order of thermal stability. A comparison of thermal stability based on Tmax for the first step also reveals a similar order. Based on T~, PCBPA seems to exhibit the highest thermal stability and PCBPS, PCBPC, PCPh, PCDN-1,5 and P C D N - I , 7 seem to follow in order of decreasing stability. All these temperature characteristics, being single feature criteria, do not provide any certain indication of relative thermal stabilities of polycyanurates. Therefore, to obtain a semiquantitative picture of relative thermal stability, an integral procedural decomposition temperature [20] (IPDT) is calculated for each polycyanurate and is presented in Table 2. The IPDT was calculated from the following expression: IPDT = A *(Tf - 7"1)+ T~, where A * is the fractional area under the T G A curve normalized with respect to residual weight; and Tf and Ti are temperatures of completion and initiation of weight loss, respectively. Based on IPDT values, overall relative thermal stability of polycyanurates is found to be in the following order of decreasing stability: PCBPA > PCBPC > PCPh PCBPS > P C D N - I , 5 > PCDN-1,7. Almost a similar trend of thermal stability has been observed by N a k a m u r a et al. [5] for high molecular weight polycyanurates derived from D P A D C T . These studies reveal that the thermal stabilities of polycyanurates are significantly related to the
195
aromatic diol component of the molecular chain and that polycyanurates of enhanced stability may be derived from aromatic diols of the type HO--Ph--X--Ph--OH where X = C ( C H 3 ) 2 and cyclohexyl. Introduction of phthalide or sulphone groups in the polycyanurate backbone is not advantageous since C - - O and C - - S bonds are more thermolabile than to C - - C . Acknowledgement--R. B. Naik is grateful to Professor H. B.
Naik for encouragement. REFERENCES
1. R. Audebert and J. Nee'l. Compte Rendu 258, 4749 (1964). 2. R. Audebert and J. Nee'l. J. Polym. Sci. C16, 3245 (1968). 3. V. V. Korshak. Soobshch. Akad. Nauk. gruz. SSR 46, 353 (1967). 4. Y. A. Murave'o. Trudf mosk. Khim. tekhnol. Inst. 52, 159 (1967). 5. Y. Nakamura, K. Mori, K. Tamura and Y. Saito. J. Polym. Sci. A 1 7, 3089 (1969). 6. G. Allen and A. G. De Boos. Polymer, 15, 56 (1974). 7. J. Fontanyanes, E. Santi and S. G. Babe. Rev. Plast. Med. 21, 477 (1970). 8. P. P. Shah. Eur. Polym. J. 20, 519 (1984). 9. P. P. Shah. J. macromolec. Sci., Chem. Edn A21, 715 (1984). 10. P. H. Parsania, P. P. Shah, P. C. Patel and R. D. Patel. J. macromolec. Sci., Chem. Edn A22, 1495 (1985). 11. N. A. Shah and P. P. Shah. J. Macromolec. Sci., Phys. Edn B23, 383 (1985). 12. J. T. Thurston and J. R. Dudley. J. Am. chem. Soc. 73, 2981 (1951). 13. I. K. Sempuku. Chem. Abstr. 97, 91,937 (1982). 14. A. Weissberger. Technique of Organic Chemistry, 3rd edn., Part 1, Vol 182 (1959). 15. E. Z. Casassa, D. Y. Chao and M. Henson. J. Macromolec Sci., Chem. Edn A15, 799 (1981). 16. G. L. Slonimskii, A. A. Askadskii and A. T. Kitaigorodskii. Polym. Sci. USSR 12, 556 (1970). 17. K. Tamura, I. Nakamura and Y. Nakamura. Kogyo Kagaku Zasshi 68, 1625 (1965). 18. W. M. Padgett and W. F. Hammer. J. Am. chem. Soc. 80, 803 (1957). 19. M. M. Koton and Yu. N. Sazanov. Polym. Sci. USSR 15, 1857 (1974). 20. C. D. Doyle. Analvt. Chem. 33, 77 (1961).
0014-3057/89 $3.00+0.00 Copyright © 1989 Pergamon Press plc
SYNTHESIS A N D PROPERTIES OF SOME POLYCYANURATES R. B. NAIK* and P. P. SHAH Department of Chemistry, South Gujarat University, Surat-395 007, Gujarat, India (Received 14 April 1988)
Abstract--Six polycyanurates were synthesized by stirred interfacial polycondensation of 2-diphenylamino-4,6-dichloro-s-triazine with each of the aromatic diols, bisphenol-A: bisphenol-C; bisphenol-S; phenolphthalein; 1,5- and 1,7-dihydroxynaphthalene. The polycyanurates, obtained in 60-80% yield, possessed reduced viscosities in the range 0.1~3.19 dl/g and were soluble in chlorinated solvents such as chloroform, dichloroethane and methylene chloride. The polycyanurates were characterized by i.r. spectra. The density and thermal stability of each of the polycyanurates were also determined. Polycyanurates derived from bisphenol-A and bisphenol-C were found to possess greater thermal stability than the others.
INTRODUCTION Polycyanurates derived from 2-R-4,6-dichloro-striazine and aromatic diols have gained importance in the field of thermally stable polymers. Earlier attempts [I-4] based on high temperature solution polycondensation led to formation of low molecular weight, insoluble and infusible polycyanurates. The stirred interracial polycondensation technique has been reported to yield high molecular weight polycyanurates [5-11]. Polycyanurates are noted for high transition temperatures and thermal stabilities. In the present investigation, polycyanurates synthesized by interracial polycondensation of 2-diphenylamino-4,6-dichloro-s-triazine (DPADCT) with each of several aromatic diols viz. bisphenol-A (BPA), bisphenol-C (BPC), bisphenol-S (BPS), phenolphthalein (Ph), 1,5- and 1,7-dihydroxynaphthalene (DN-1,5 and DN-1,7) are reported. The polycyanurates have been characterized by viscosity, solubility, density, i.r. spectroscopy and thermogravimetry.
aqueous solution and the emulsion was stirred vigorously for 5 hr at 25°. The organic layer containing the polymer was isolated and washed with water; polymer was precipitated from methanol. It was filtered, washed with water, methanol, and finally with acetone. The yield of the dried polymer was 78%. The polymer was further purified by dissolving in chloroform followed by reprecipitation from petroleum ether. A solution of the polymer in chloroform (1 g/dl) had a reduced viscosity of 0.19 at 30°. Other polycyanurates (see Table I), were prepared by this procedure. Characterization methods Reduced viscosities of polycyanurates were determined for 1 g/dl solutions in chloroform at 30° using an Ubbelohde suspended level viscometer. The densities of polycyanurates were determined using suspension method [14]. The liquid system used was carbon tetrachloride and petroleum ether. i.r. Spectra of the polycyanurates were recorded on a Perkin-Elmer i.r. spectrophotometer using a KBr pellet technique. Thermogravimetric analyses (TGA) of the polycyanurates were performed using a Mettler TA 3000 system at a heating rate of 10°/min in air.
RESULTS AND DISCUSSION
EXPERIMENTAL Materials DPADCT was synthesized by the reported method [12] and purified by crystallization from ethanol (m.p. 172°). BPA was crystallized from benzene (m.p. 156~). BPC [10] and BPS [13] were synthesized by published methods and were crystallized from benzene (m.p. 187 and 239° for BPC and BPS, respectively). Commercially available phenolphthalein (BDH), DN-I,5 and DN-1,7 (Sisco Lab) were purified by crystallization. Benzyl dimethyl hexadecylammonium chloride (BDMHDACI) (BDH) was used as received. AR grade solvents were used. Synthesis of polycyanurates A typical example of interfacial polycondensation is given below for the formation of polycyanurate of BPA. A solution of BPA (2.28g, 0.01 moll NaOH (0.8g 0.02mol) and BDMHDACI (0.125g) in distilled water (50 ml) was stirred at 25~. A solution of DPADCT (2.17 g, 0.01 mol) in chloroform (25 ml) was rapidly added to the
*To whom correspondence should be addressed.
Several characteristics of polycyanurates are now reported (Table 1). The interface system used a good solvent (chloroform). Polycyanurate formation was found to be possible only with the use of cationic emulsifier. Both surfactant and catalytic functions could be combined through the use of cationic surfactants which, as quaternary a m m o n i u m compounds, could aid in transfer of monomer between phases [15]. Cation emulsifiers have been exclusively used for the synthesis of polycyanurates [5, 8-11]. Examination of reduced viscosity values reveals that, among chloroform soluble polycyanurates, PCBPA has the highest whereas PCBPS has the lowest solution viscosity. The trend of these values reflect order of relative reactivity of bisphenols. BPA is the least acidic and hence most reactive towards nucleophilic displacement reaction and hence leads to the formation of polycyanurate of a comparatively higher molecular weight. Due to electronic effects BPS is highly acidic and hence least reactive and 193
R. B. NAIK and P. P. SHAH
194
Table 1. Characteristics of polycyanuratesderived from DPADCT Polymer Yield ~lsp/C= Aromatic code (%) (ml/g) d (g/cm3) dial 75 19.0 1.218 Bisphenol-A PCBPA 75 17.0 1.202 BisphenoI-C PCBPC 60 5.0 1.327 BisphenoI-S PCBPS 67 7.0 1.278 Phenolphthalein PCPh 65 18.0b 1.254 1,5-Dihydroxynaphthalene PCDN-1,5 65 16.0b 1.278 1,7-Dihydroxynaphthalene PCDN-1,7 ~Chloroform, 30% bN,N'-dimethylformamide,30°. leads to lower molecular weight polycyanurate. Of the two isomeric dihydroxy naphthalenes, the 1,5isomer seems to be more reactive probably because of its greater symmetry.
Densities of polycyanurates Densities of polycyanurates determined at 25 ° by suspending each of the polycyanurates in a mixture of carbon tetrachloride and petroleum ether and subsequently measuring the density of the liquid mixture by a pyknometer are also presented in Table 1. Densities, calculated theoretically on the basis of the structural concept proposed by Slonimskii et al. [15] are also presented; an average value of 0.684 for packing coefficient, k, was used for this calculation; k was approximated from the slope of a line best fitting the
d (calc.) (g/cm3) 1.200 1.197 1.315 1.268 1.256 1.256
liii . . 4
:"l
;6o
F
d - M /NA ~ AV, i
curve [15]. Volume increments, Al/i, of relevant atomic groups making up the polycyanurate repeat unit have been calculated by us and used by calculate intrinsic volume. Comparison of experimental and calculated densities shows a good correlation.
AI/i (A3) 446.6 485.6 426.5 503.2 365.4 365.4
0
f
3
100 zoo 300
400
500
6oo
,
700
Temperature ("C] Fig. 1. TGA thermograms at a heating rate of 10°/min in air (1) PCBPA, (2) PCBPC, (3) PCBPS, (4) PCPh, (5) PCDN-1,5 and (6) PCDN-1,7.
i.r. Spectral characteristics The i.r. spectra of these polycyanurates exhibited the following c o m m o n characteristic absorption frequencies (cm -~) at 815-830 and 1670-1430 attributable to out-of-plane and in-plane vibrations of s-triazine ring, respectively, at 1300-1240 attributed to vibrations involving aryl-ether linkage [16-18]. In addition, the spectra exhibited a few absorption frequencies based on which these polycyanurates can be distinguished from one another. These frequencies (cm-~ ) are: 420, 550 ( C - - C deformation vibrations of propyl link), 1180 ( C - - C skeletal vibrations of propyl link), 1375 and 1385 (both of nearly equal intensity due to C - - C H 3 deformations of propyl group) for PCBPA; 535, 940, 980 (all C---C deformation vibrations of cyclohexane ring) for PCBPC: 570, 590
(scissoring vibrations of sulphone group), 1160 and 1370 (symmetric and assymetric stretching vibrations of sulphone group) for PCBPS; 780, 1085 (odisubstituted phenyl ring), 1775 ( C - - O stretching of lactone group) for PCPh. Spectral distinction between PCDN-1,5 and PCDN-1,7 which may be based on frequencies in the region 1650-1600 and 1630-1575 where ring stretching vibrations of substituted naphthalenes appear, was found to be difficult since these regions were heavily crowded by ring stretching vibrations of phenyl rings.
Thermal characteristics of polycyanurates T G A thermograms of polycyanurates are shonw in Fig. 1. Several temperature characteristics such as To
Table 2. Temperature CC) characteristics of polycyanurates Residue Polymer TO T,0 Step-I Step-ll Step-Ill T, IPDT at 700" PCBPA 350 415 425 605 -510 602 3.0 PCBPC 360 405 420 525 -470 552 11.0 PCPh 230 290 280 360 545 440 515 17.0 PCBPS 290 360 370 535 -505 510 40.0 PCDN-I,5 100 145 160 440 -195 330 35.0 PCDN-1,7 100 145 180 --185 305 18.0 T0--initial decomposition temperature; T)0--temperaturefor 10% wt loss; Tm.,--temperature for maximum rate of decomposition; T,--temperature for half volatilization;IPDT--integral procedural decompositiontemperature.
Polycyanurates--synthesis and properties (initial decomposition temperature), 7"10(temperature for 10% wt loss), Tmax (temperature for maximum rate of decomposition) and Ts (half-volatilization point temperature), which may be used for qualitative assessment of relative thermal stabilities of polycyanurates, are presented in Table 2. With dynamic heating, To and Tl0 are some of the main criteria for thermal stability of polymers. The higher the values of To and T~0, the greater the heat stability of a given polymer [19]. Comparison of T o and/or T~o for polycyanurates indicates that the thermal stabilities of PCBPA and PCBPC are quite similar and that PCBPS, PCPh, P C D N - I , 5 and P C D N - I , 7 follow the former in decreasing order of thermal stability. A comparison of thermal stability based on Tmax for the first step also reveals a similar order. Based on T~, PCBPA seems to exhibit the highest thermal stability and PCBPS, PCBPC, PCPh, PCDN-1,5 and P C D N - I , 7 seem to follow in order of decreasing stability. All these temperature characteristics, being single feature criteria, do not provide any certain indication of relative thermal stabilities of polycyanurates. Therefore, to obtain a semiquantitative picture of relative thermal stability, an integral procedural decomposition temperature [20] (IPDT) is calculated for each polycyanurate and is presented in Table 2. The IPDT was calculated from the following expression: IPDT = A *(Tf - 7"1)+ T~, where A * is the fractional area under the T G A curve normalized with respect to residual weight; and Tf and Ti are temperatures of completion and initiation of weight loss, respectively. Based on IPDT values, overall relative thermal stability of polycyanurates is found to be in the following order of decreasing stability: PCBPA > PCBPC > PCPh PCBPS > P C D N - I , 5 > PCDN-1,7. Almost a similar trend of thermal stability has been observed by N a k a m u r a et al. [5] for high molecular weight polycyanurates derived from D P A D C T . These studies reveal that the thermal stabilities of polycyanurates are significantly related to the
195
aromatic diol component of the molecular chain and that polycyanurates of enhanced stability may be derived from aromatic diols of the type HO--Ph--X--Ph--OH where X = C ( C H 3 ) 2 and cyclohexyl. Introduction of phthalide or sulphone groups in the polycyanurate backbone is not advantageous since C - - O and C - - S bonds are more thermolabile than to C - - C . Acknowledgement--R. B. Naik is grateful to Professor H. B.
Naik for encouragement. REFERENCES
1. R. Audebert and J. Nee'l. Compte Rendu 258, 4749 (1964). 2. R. Audebert and J. Nee'l. J. Polym. Sci. C16, 3245 (1968). 3. V. V. Korshak. Soobshch. Akad. Nauk. gruz. SSR 46, 353 (1967). 4. Y. A. Murave'o. Trudf mosk. Khim. tekhnol. Inst. 52, 159 (1967). 5. Y. Nakamura, K. Mori, K. Tamura and Y. Saito. J. Polym. Sci. A 1 7, 3089 (1969). 6. G. Allen and A. G. De Boos. Polymer, 15, 56 (1974). 7. J. Fontanyanes, E. Santi and S. G. Babe. Rev. Plast. Med. 21, 477 (1970). 8. P. P. Shah. Eur. Polym. J. 20, 519 (1984). 9. P. P. Shah. J. macromolec. Sci., Chem. Edn A21, 715 (1984). 10. P. H. Parsania, P. P. Shah, P. C. Patel and R. D. Patel. J. macromolec. Sci., Chem. Edn A22, 1495 (1985). 11. N. A. Shah and P. P. Shah. J. Macromolec. Sci., Phys. Edn B23, 383 (1985). 12. J. T. Thurston and J. R. Dudley. J. Am. chem. Soc. 73, 2981 (1951). 13. I. K. Sempuku. Chem. Abstr. 97, 91,937 (1982). 14. A. Weissberger. Technique of Organic Chemistry, 3rd edn., Part 1, Vol 182 (1959). 15. E. Z. Casassa, D. Y. Chao and M. Henson. J. Macromolec Sci., Chem. Edn A15, 799 (1981). 16. G. L. Slonimskii, A. A. Askadskii and A. T. Kitaigorodskii. Polym. Sci. USSR 12, 556 (1970). 17. K. Tamura, I. Nakamura and Y. Nakamura. Kogyo Kagaku Zasshi 68, 1625 (1965). 18. W. M. Padgett and W. F. Hammer. J. Am. chem. Soc. 80, 803 (1957). 19. M. M. Koton and Yu. N. Sazanov. Polym. Sci. USSR 15, 1857 (1974). 20. C. D. Doyle. Analvt. Chem. 33, 77 (1961).