Preparation and polymerization behavior of 2,4-dicyanostyrene and 2,4,6-tricyanostyrene

Macromolecules 1989, 22, 38-45 Downloaded by HENKEL KGAA on August 18, 2009 Published on January 1, 1989 on http://pubs.acs.org | doi: 10.1021/ma00191a008 38 distribution will be considered. In conclusion, we have demonstrated the pronounced effect of laser repetition rate on the molecular weight distribution of photopolymerized methyl methacrylate. The narrow peaks found in the GPC chromatogram of poly(methy1 methacrylate) generated by firing the laser at a repetition rate of 40 Hz (25 ms between successive pulses) have been initially described by a simple kinetic model based upon a series of Poisson distribution functions. Complete details of the computer simulation of the molecular weight distributions as a function of pulsing frequency as well as several refinements to our current approach, will be published in a full paper. This paper serves to provide a basis for describing the crucial effect of laser parameters on the polymerization of monofunctional monomers. Extension of this work to encompass multifunctional monomers is in progress. Acknowledgment. This research is supported by National Science Foundation Grant DMR 85-14424 (Polymers Program). Acknowledgement is also made to NSF for assistance in purchasing the laser system utilized in the course of this investigation (Grant CHE-8411829Chemical Instrumentation Program). Registry No. PMMA, 9011-14-7. References and Notes (1) Decker, C. J . Polym. Sci., Polym. Chem. Ed. 1983,21,2451. (2) Decker, C. J . Coat. Tech. 1984,56,29. (3) Decker, C. Polym. Prepr. 1984,25,303. (4) Decker, C. ACS Symp. Ser. 1984,No. 266,207. (5) Decker, C.Polym. Mat. Sci. Eng. 1983,49,32. (6) Decker, C.;Moussa, K. Polym. Mat. Sci. Eng. 1986,552. (7) Decker, C. Radcure Proceedings, FC 1983,83-265. (8) Fouassier, J. P.; Jacques, P.; Lougnot, D. L.; Pilot, T. Polym. Photochem. 1984,5,57. (9) Williamson, M. A.;Smith, J. D. B.; Castle, P. M.; Kauffman, R. N. J. Polym. Sci., Polym. Chem. Ed. 1982,20,1875. (10) Sadhir, R. K.; Smith, J. D. B.; Castle, P. M. J. Polym. Sci., Polym. Chem. Ed. 1983,21,1315. (11) Burback, M.; Hippler, H.; Schweer, J.; Vogele, H.-P. Makromol Chem., Rapid Commun. 1986,7,261. (12) Brackemann, H.; Buback, M.; Schweer, J.; Tups, H.; Vogele, H.-P. ChemJng. Tech. 1987,59,598. (13) Buback, M.; Huckestein, B.; Leinhos, U. Makromol. Chem., Rapid Commun. 1987,8,473. (14) Buback, M.; Schweer, J. Makromol. Chem., Rapid Commun. 1988,9, 145. (15) Olaj, 0. Bitai, I.; Gleixner, G. Makromol. Chem. 1985,186, F.; 2569. (16) Olaj, 0. Bitai, I.; Hinkelmann, F.Makromol. Chem. 1987, F.; 188,1689. . Bitai, I. Angew. Makromol. Chem. 1987,155, 177. (17) Olaj, 0 F.; (18) Hoyle, C. E.;Hensel, R. D.; Grubb, M. B. J. Polym. Photochem. 1984,4,69. (19) Hoyle, C. E.; Hensel, R. D.; Grubb, M. B. J. Polym. Sci., Polvm. Chem. Ed. 1984.22. 1965. (20) Hoyle, C. E.; Hense1,'R. D.; Grubb, M. B. J. Radiat. Curing 1984,11(4),22. (21) Peebles, L. H., Jr. Molecular Weight Distributions in Polymers: Interscience: New York, 1971. Preparation and Polymerization Behavior of 2,4-Dicyanostyrene and 2,4,6-Tricyanostyrene Shouji Iwatsuki,* Takahito Itoh, Yoshiki Shimizu, and Takashi Enomoto Department of Chemical Research for Resources, Faculty of Engineering, Mie University, Kamihama-cho, Tsu 514, Japan. Received February 12, 1988 ABSTRACT: 2,4-Dicyanostyrene (DCS) was successfully prepared in 18% yield via a series of six reactions and 2,4,6-tricyanostyrene (TCS) was barely in 0.15% yield via five reaction steps. It was found that DCS and TCS are polymerizable with radical and anionic initiators. DCS and TCS are copolymerizable in a random and an alternating fashion, respectively, with styrene (St) in the presence of 2,2'-azobis(isobutyronitrile) (AIBN) in acetonitrile to afford the monomer reactivity ratios rl(DCS) = 1.85 f 0.03 and rz(St) = 0.08 f 0.03 for the DCS-St system at 60 O C and r,(TCS) = 0.02 i 0.02 and rz(St) = 0.04 i 0.01 for the TCS-St system a t 60 "C. By using these values, the Alfrey-Price's Q and e values were determined to be Q = 4.10 and e = +0.58 for DCS and Q = 2.83 and e = +1.86 for TCS. When DCS or TCS was mixed with p-(dimethy1amino)styrene (DMASt), the former system was colored pale yellow and did not undergo further reaction, while the latter one was colored red and underwent spontaneous reaction to give polymeric product containing homopolymers of TCS and DMASt, suggesting that anionic polymerization of TCS and cationic one of DMASt occur at the same time. Introduction Only a few compounds have been reported of the electron-accepting group substituted styrenes carrying more than two strongly electron-withdrawing groups on the benzene nucleus, such as 2,4,6-trinitrostyrene (TNS),1-3 2,4,6-tris(trifluoromethyl)styrene(TFS),4 2,5-, 3,5-, and and 3,4-bis(trifluoromethyl)styrenes.6 Although the cyano (up = 0.674)6group is strongly electron withdrawing and its character is just intermediate between that of nitro (up = 0.778)6 and trifluoromethyl (ap = O l ~ 3 2 groups, poly)~ cyano-substituted styrenes have not yet been found in any literature, but 0-,m-, and p-monocyanostyrenes7-9were 0024-9297/89/2222-0038$01.50/0 reported. In addition, because the cyano group appears to be almost insensitive to free radical species compared with the nitro group, it was expected that polycyanosubstituted styrenes would be readily polymerizable with a free radical initiator while TNS is not so polymerizable.'P2 In this work, 2,4-dicyanostyrene (DCS) and 2,4,6-tricyanostyrene (TCS) were first prepared as new polycyanosubstituted styrenes, and their polymerization behaviors were studied. Experimental Section p-Bromoethylbenzene ()O 1) p-Bromoacetophenone (83.7g, 0.42 mol) was reduced with zinc amalgam" which was prepared 0 1989 American Chemical Society Macromolecules, Vol. 22, No. I, 1989 HC=CHp @CN CN Downloaded by HENKEL KGAA on August 18, 2009 Published on January 1, 1989 on http://pubs.acs.org | doi: 10.1021/ma00191a008 DCS HC=CH2 N J +C C N CN TCS from 170 g (2.60 mol) of mossy zinc and 17 g (0.063 mol) of mercuric chloride12 to obtain 59.2 g (in 76% yield) of colorless boiling at 87-88 "C under pressure oily p-bromoethylbenzene (l), of 18 mmHg (lit.lo bp 188-189 OC): 'H NMR (CC14)6 1.20 (t, J = 7.5 Hz, 3 H), 2.57 (q, J = 7.5 Hz, 2 H), 6.97 (d, J = 7.5 Hz, 2 H), 7.33 (d, J = 7.5 Hz, 2 H). p-Ethylbenzonitrile (2)>3 The compound 1 (59.2 g, 0.32 mol) was reacted with 34.4 g (0.38 mol) of copper(1) cyanide in 50 mL of Nfl-dimethylformamide (DMF) under refluxing for 6 h to obtain 38.0 g (in 88% yield) of colorless oily p-ethylbenzonitrile (2) boiling at 84-86 "C under pressure of 5 mmHg: IR (NaC1) u(CN) 2240 cm-'; 'H NMR (CClJ 6 1.25 (t, J = 7.5 Hz, 3 H), 2.70 (q, J = 7.5 Hz, 2 H), 7.23 (d, J = 7.5 Hz, 2 H), 7.73 (d, J = 7.5 Hz, 2 H). 3-Bromo-4-ethylbenzonitrile(3). The compound 2 (14.1 g, 0.11 mol) was reacted with 19.8 g (0.12 mol) bromine in the presence of 46.9 g (0.35 mol) of finely powdered anhydrous aluminum chloride to give 18.5 g (in 81.5% yield) of colorless oily 3-bromo-4-ethylbenzonitrile (3), boiling at 83-85 "C under pressure of 1.5 mmHg, which crystallized on standing for a long time: mp 43.5-45.0 "C: IR (NaC1) v(CN) 2220, u(CH) 880, 835 cm-l; 'H NMR (CCl,) 6 1.23 (t,J = 7.5 Hz, 3 H), 2.77 (q, J = 7.5 Hz, 2 H), 7.2-7.7 (m, 3 H). Anal. Calcd for CgH&rN H, 3.84, C, 51.46; N, 6.67; Br, 38.03. Found H, 3.67; C, 51.07; N, 6.45; Br, 38.81. 2,4-Dicyano-l-ethylbeneene The compound 3 was re(4). acted with copper(1) cyanide in DMF under refluxing for 6 h to give crystalline material which was recrystallized from hexane to obtain white needles: mp 72.5-73.5 "C; IR (KBr) u(CN) 2230, u(CH) 890,840 cm-'; 'H NMR (CC14)6 1.37 (t, J = 7.5 Hz, 3 H), 2.95 (9, = 7.5 Hz, 2 H), 7.3-7.9 (m, 3 H). Anal. Calcd for J C1$18N2: H, 5.16; C, 76.90; N, 17.94. Found H, 5.02; C, 76.51; N, 17.86. 1-( l-Bromoethyl)-2,4-dicyanobenzene The compound (5). 4 (10.0 g, 0.064 mol) was brominated with 12.1 g (0.038 mol) of N-bromosuccimide (NBS) in the presence of 0.05 g of AIBN in 80 mL of carbon tetrachloride under refluxing for 24 h to give a brown solid which was recrystallized from isopropyl ether to obtain 11.2 g (in 70.4% yield) of pale orange needles of 5: mp 90-91 "C; IR (KBr) v(CN) 2225, a(CH) 900,860 cm-'; 'H NMR (CCl,) 6 2.09 (d, J = 7.5 Hz, 3 H), 5.48 (q, J = 7.5 Hz, 1 H), 7.58-8.20 (m, 3 H). Anal. Calcd for Cl&17N2Br: H, 3.00, C, 51.09; N, 11.92;Br, 33.99. Found H, 3.08; C, 51.43; N, 12.05;Br, 33.44. 2,4-Dicyanostyrene (DCS). Compound 5 (3.9 g, 16.6 mmol), 5.4 g (53.8 mmol) of triethylamine, and 5 mg of 4-hydroxy2,2,6,6-tetramethylpiperidinyloxy (TEMPOL) as a radical polymerization inhibitor were dissolved in 20 mL of acetonitrile and the solution was refluxed with stirring under nitrogen for 9 h. The reaction mixture was placed under reduced pressure to give a brown solid, which was dissolved in 30 mL of chloroform. The resulting solution was washed with two 10-mL portions of water and two 10-mL portions of 5% sodium hydroxide solution and dried over anhydrous magnesium sulfate. It was placed under reduced pressure to evaporate the solution until its volume amounted to about 5 mL. The concentrate was passed through a column of 2-cm diameter and 20-cm length packed with silica gel, using chloroform as eluent. The first elution band was collected and placed under reduced pressure to obtain 1.8 g of white solid, which was recrystallized from dry ethanol to give 1.7 g (in 67.5% yield) of white needles of DCS, which is soluble in benzene, toluene, acetone, chloroform, tetrahydrofuran (THF), and acetonitrile and sparingly soluble in isopropyl ether and hexane: mp 155-156 "C; UV (CH,CN) 267 nm (c 1.55 X lo4);IR (KBr) u(C=C) 1595, a(CH) 900, 845 cm-'; 'H NMR (CDC13) 6 5.79 (d, J = 11.4 Hz, 1 H), 6.14 (d, J = 17.44 Hz, 1 H), 7.14 (dd, J = 17.4 and 11.4 Hz, 1 H), 7.80 (s,2 H), 7.93 ( 8 , 1 H). Anal. Calcd for C&I&: H, 3.92; C, 77.91;N, 18.17. Found H, 4.00; C, 77.85; N, 18.15. 2,6-Dibromo-4-cyanotoluene p-Tolunitrile (6) (25 g, 0.26 (7). Preparation and Polymerization of DCS and TCS 39 mol) was brominated with 85.2 g (0.53 mol) of bromine in the presence of 90.7 g (0.68 mol) of finely divided anhydrous aluminum chloride 70-80 "C for 7 h. The reaction mixture was poured into 500 mL of ice water containing 100 mL of concentrated hydrochloric acid. The mixture was extracted with four 2WmL portions of toluene. The combined extract was washed and evaporated to obtain a liquid residue which was fractionally distilled under pressure of 0.5 mmHg to obtain 30.5 g of the fraction boiling at 80-100 "C and 28.1 g of the fraction boiling above 100 "C. The latter fraction was recrystallized three times from isopropyl ether to give 17.1 g (in 29.2% yield) of pale brown needles of 7: mp 95-98 "C; IR (KBr) u(CN) 2240, v ( M ) 1530,1450c - ; NMR m ' 'H (CDC13) 6 2.63 (9, 3 H), 7.80 (5, 2 H). 2,4,6-Tricyanotoluene (8). Compound 7 (20.0 g, 0.073 mol) was reacted with 15.5 g (0.173 mol) of copper(1) cyanide in 100 mL of DMF under refluxing for 12 h. The reaction mixture was slowly poured into 500 mL of water to deposit dark green solid which was suspended in the solution composed of 60 g of ferric chloride hexahydrate, 15 mL of concentrated hydrochloric acid, and 100 mL of water. The resulting suspension was kept warm at 100 "C with stirring for 6 h and extracted with two 200-mL portions of toluene. The combined extract was washed with two 50-mL portions of 5% hydrochloric acid, two 50-mL portions of 10% sodium hydroxide solution, and two 100-mL portions of water and then dried over anhydrous magnesium sulfate. It was placed under reduced pressure to obtain 2.5 g of yellow solid, which was recrystallized from a mixture of dichloromethane and hexane to give 2.4 g (in 19.2%yield) of pale yellow needles of 8 mp 132-133 "C; IR (KBr) u(CN) 2240, v ( W ) 1465, a(CH) 925 cm-'; 'H NMR (CDC13)6 2.87 (s, 3 H), 78.11 ( s , 2 H). Anal. Calcd for C185N3: H, 3.02; C, 71.84; N, 25.14. Found H, 2.67; C, 72.72; N, 24.61. 2,4,6-Tricyano-l-ethylbenzene The solution of 1.0 g (6.0 (9). mmol) of 8 and 2.8 g (24.1 mmol) of N,N,N',N'-tetramethylethylenediamine (TMEDA) in 50 mL of THF was added dropwise into the solution of 24 mmol of lithium diisopropylamide (LDA) in 100 mL of T H F cooled to -78 "C with stirring. The resulting dark red solution was kept cold at -78 "C with stirring for 1 h, and 8.7 g (61.0 mmol) of methyl iodide was added. Furthermore, it was kept cold at -78 "C with stirring for an additional 1 h and, then, warmed slowly to room temperature. It was placed under reduced pressure to remove solvents, and the residual brown solid was dissolved in 100 mL of dichloromethane. The solution was washed with two 50-mL portions of 5% hydrochloric acid and two 50-mL portions of water and then dried over anhydrous magnesium sulfate. I t was placed under reduced pressure to remove solvents and the residue was chromatographed over silica gel by using dichloromethane as eluent to separate a yellow portion, which was evaporated to give 0.58 g (in 53.5% yield) of yellow solid of 9: mp 123-125 "C; IR (KBr) u(CN) 2240, v(C=C) 1455, o(CH) 925 cm-'; 'H NMR (CDC1,) 6 1.41 (t, J = 7.5 Hz, 3 H), 3.20 (q, J = 7.5 Hz, 2 H), 8.13 (s, 2 H). Anal. Calcd for CllH7NS H, 3.89; C, 72.92; N, 23.19. Found: H, 2.89; C, 72.45; N, 22.65. 1- ( 1-Bromoethyl)-2,4,6-tricyanobenzene( 10). Compound 9 (1.0 g, 5.5 mmol), 1.0 g (5.8 mmol) of NBS, 5 mg of AIBN, and 40 mL of carbon tetrachloride were placed in a 100-mL flask. While the mixture was refluxed with stirring for 12 days, additional portions composed of 5 mg of AIBN and 0.5 g of NBS were added every day. The hot mixture was filtered to remove solid material such as succinimide. The filtrate was placed under reduced pressure to obtain brown viscous residue, which was dissolved in 30 mL of chloroform, and the resulting solution was washed with three 50-mL portions of water and dried over anhydrous magnesium sulfate. It was placed under reduced pressure to yield pale brown viscous material, which was recrystallized from isopropyl ether to give 0.65 g (in 45% yield) of colorless crystal of 1 0 mp 125-127 "C; I (KBr) u(CN) 2240,u(C=C) 1465,u(CH) R 930 cm-'; 'H NMR (CDCl,) 6 2.29 (d, J = 7.5 Hz, 3 H), 5.65 (q, J = 7.5 Hz, 1 H), 8.17 (s, 2 H). Anal. Calcd for C11HsN3Br: H, 2.33; C, 50.80; N, 16.14;Br, 30.73. Found: H, 2.31; C, 50.56; N, 16.25; Br, 30.88. 2,4,6-Tricyanostyrene (TCS). Compound 10 (0.3 g, 1.2 mmol), 0.2 g (2.0 mmol) of triethylamine, and 1 mg of TEMPOL were dissolved in 10 mL of acetonitrile and the solption was refluxed with stirring under nitrogen for 5 h. The reaction mixture was placed under reduced pressure to obtain dark yellow solid, Macromolecules, Vol. 22, No. 1, 1989 Downloaded by HENKEL KGAA on August 18, 2009 Published on January 1, 1989 on http://pubs.acs.org | doi: 10.1021/ma00191a008 40 Iwatsuki e t al. which was dissolved in 20 mL of chloroform. The resulting solution was washed successively with two 10-mL portions of water, two 10-mL portions of 5% sodium hydroxide solution, and 10 mL of water and, then, dried over anhydrous magnesium sulfate. It was placed under reduced pressure to remove solvents. The remaining yellow solid was dissolved in 1 mL of benzene. The resulting solution was passed through a column of 2-cm diameter and 20-cm length packed with silica gel, using isopropyl ether as eluent. The first elution band separated was placed under reduced pressure to obtain 32 mg of pale yellow solid, which was recrystallized from dry ethanol to give 22.1 mg (in 10.7% yield) of pale yellow needles of TCS, which is soluble in benzene, toluene, chloroform, THF, and acetonitrile and sparingly soluble in ethanol and hexane: mp 143-144 "C; UV (CH&N) 237 (t 3.06 X lo4), 267 nm (e 1.35 X lo4); IR (KBr) v(CN) 2240, v(C=C) 1630,1595, 1455, o(CH) 975,955,925, 780 cm-'; 'H NMR (CDCl,) 6 6.14 (d, J = 11.4 Hz, 1 H), 6.49 (d, J = 17.4 Hz, 1 H), 7.12 (dd, J = 17.4 and 11.4 Hz, 1 H), 8.14 (s, 2 H). Anal. Calcd for CllH5N3: H, 2.81; C , 73.74; N, 23.45. Found: H, 2.89; C, 74.05; N, 23.08. O t h e r Reagents. p(Dimethy1amino)styrene (DMASt), prepared according to the procedure of Strassburg et al.,14was stirred over calcium hydride for 3 h and distilled a t 91 "C under pressure of 3 mmHg. Styrene (St)was washed with 2% sodium hydroxide solution and water, dried over barium oxide for 5 h and then over calcium hydride, and distilled at 52 "C under pressure of 30 mmHg. Triethylamine and diisopropylamine were refluxed over calcium hydride for 5 h and distilled a t 88.5 and 82 " C , respectively. T H F was refluxed over lithium aluminum hydride for 12 h and then distilled a t 66 O C over benzophenone-metal sodium. Benzene, acetonitrile, and carbon tetrachloride were purified from commercial products according to conventional methods. AIBN was recrystallized from ethanol. Butyllithium (Aldrich Co.) was used without further purification. Tetrabutylammonium perchlorate was dried a t 150 "C under pressure of 0.01 mmHg for 16 h. Methyl iodide was distilled a t 42.5 "C under dark conditions. Isophthalonitrile (DCB) was recrystallized from benzene. 1,3,5Tricyanobenzene (TCB) was prepared according to the method of Bailey et al.15 and recrystallized from ethanol. Polymerization Procedure. In the case of radical polymerization with AIBN, given amounts of DCS or TCS as monomer, acetonitrile or benzene as solvent, and AIBN were placed in an ampule, which was degassed by the freeze-thaw method (repeatedly three times) and sealed. The ampule was set in a bath thermostated a t 60 "C for the time of polymerization and then opened. The reaction mixture was poured into an excess methanol to precipitate the polymer. For purification, the polymer obtained was dissolved again in a small amount of acetonitrile and the resulting solution was poured into excess methanol to precipitate the polymer, which was dried under reduced pressure. In the case of polymerization with butyllithium, the apparatus reported in the previous paper16 was employed. Given amounts of DCS or TCS as monomer and T H F as solvent were placed in the apparatus which was degassed by the freeze-thaw method (repeatedly three times) and then filled with argon. Into the apparatus immersed in an ice-water bath, a given amount of butyllithium in THF was injected by means of a syringe. After 24 h, the reaction mixture was poured into exces hexane to deposit the polymer. The rest of the procedure was similar to above mentioned one for the polymerization with AIBN except for using THF and hexane instead of acetonitrile and methanol as solvent and precipitant for purification. In the case of copolymerizations of the DCS-St, TCS-St, and DCS-DMASt systems, given amounts of DCS or TCS as monomer, St or DMASt as comonomer, acetonitrile as solvent, and 0.5 mol % AIBN to the total monomer were placed in an ampule, which was degassed by the freeze-thaw method and sealed. The ampule was set in a bath thermostated a t 60 "C for the time of polymerization and then opened. The reaction mixture was poured into an excess methanol to precipitate the copolymer. The rest of the procedure was similar to above-mentioned one for the radical polymerization. In the case of the reaction of the TCS-DMASt system without initiator, 28.6 mg of TCS and 55.1 mg of DMASt were placed in an ampule, which was degassed by the freeze-thaw method and sealed. The ampule was kept at room temperature for 98 h and then opened. The reaction mixture was divided into four fractions Scheme I CH3 c=o CH2CH3 I I CN 3 CH2CH3 I CN 4 CN 5 by the dissolution-precipitation process as follows: The reaction mixture was dissolved in 5 mL of THF and the resulting solution was poured into 100 mL of isopropyl ether to give a suspension, which was separated into supernatant and precipitate by centrifugation. The isopropyl ether solution as supernatant was placed under reduced pressure to remove solvents. Viscous material (36 mg) as fraction I was obtained. The precipitate (26 mg) was dissolved again in 5 mL of THF and the resulting solution was poured into 100 mL of methanol to give the second suspension. The methanol solution as supernatant was placed under reduced pressure to remove solvents. Solid residue (4.5 mg) as fraction I1 was obtained. The precipitate (21.5 mg) was dissolved in 10 mL of T H F and the resulting solution was poured into 100 mL of methanol to give 8.1 mg of a precipitate as fraction IV. The filtrate was evaporated under reduced pressure to give 13.3 mg of pale yellow solid material as fraction 111. Characterization. Voltammetric measurement was carried out a t room temperature by using a Yanagimoto new cyclic voltammetric analyzer VMA-010 instrument. Dichloromethane containing tetrabutylammonium perchlorate (0.1 mol/L) as solvent, a glassy carbon as working electrode, and a platinum wire as third electrode were used. Copolymer composition was established by elemental analysis. The number-average molecular weight, M,, of the polymers and the copolymers was determined without correction by gel permeation chromatography (GPC) using standard polystyrene as reference and THF as eluent. Solution viscosity was determined a t 30 "C by using the Ostwald viscometer and acetone for the polymer of DCS and THF for the copolymer of the DCS-St system as solvent. In 'H NMR measurement solvents employed were acetone-d6 for the polymers of DCS and TCS and chloroform-d for the fractions of the reaction product of TCS with DMASt. Results and Discussion Preparation of DCS. DCS was successfully prepared via a series of six reactions as shown i n the Scheme I. p-Bromoacetophenone was subjected to the Clemensen reduction t o give 1 in 76% yield. The compound 1 underwent the Rosenmund-von Brawn reaction to yield 2 in 88% yield. T h e compound 2 was brominated with Friedel-Crafts catalyst to obtain 3 in 81.5% yield. The compound 3 was again subjected to the Rosenmund-von Brawn reaction to give 4 i n 76% yield, which was brominated with NBS i n the presence of AIBN to give 5 in 70% yield. Finally, the compound 5 was subjected to dehydrobromination with triethylamine i n the presence of a small amount of TEMPOL as a free radical scavenger in refluxing acetonitrile to give DCS in 67.5% yield without polymer of DCS. T h e overall yield of DCS was 18%. When dehydrobromination of 5 was carried o u t without a n y free radical scavenger, only the polymer of DCS was obtained instead of the monomer. When picric acid, 4tert-butylcatechol, and hydroquinone were used instead Macromolecules, Vol. 22, No. 1, 1989 Preparation and Polymerization of DCS and TCS 41 Scheme I1 Table I First Reduction Potential: E , , and Electron Affinity, EA, of 2,4,6-Tricyanostyrene (TCS), 2.4-Dicyanostyrene (DCS), 1,3,5-Tricyanobenzene(TCB), and 1,3-Dicyanobenzene (DCB) comvound E I s b V EA,‘eV comvound E,?V EA,CeV -1.65 1.42 1.78 DCS TCS -1.29 DCB -1.88 1.19 -1.50 1.57 TCB 3 BrgBr “TcN “qcN CH3 1 2 191.6 31.4 30.4 3 Downloaded by HENKEL KGAA on August 18, 2009 Published on January 1, 1989 on http://pubs.acs.org | doi: 10.1021/ma00191a008 CuCN “QCN TMEDA \ \ I I CN 6 CN CN 7 CHzCH3 8 BrCHCH3 I I A IB SN NB TEMPOL EtgN _c of TEMPOL the yield of monomeric DCS was as low as 20-4070, and the polymer of DCS was formed in above 50% yield. Preparation of TCS. Preparation of TCS was carried out even in a low total yield via a series of five reaction steps as shown in the Scheme 11. p-Tolunitrile (6) was brominated in the presence of anhydrous aluminum chloride at room temperature to give a mixture of 2bromo-4-cyanotoluene, 2,6-dibromo-4-cyanotoluene (7), and 2,3,6-tribromo-4-cyanotoluene. was fractionally It distilled under the reduced pressure of 0.5 mmHg to give the fraction boiling at 80-100 “C, mainly composed of 2-brome4-cyanotoluene,and the fraction boiling above 100 “C, composed of 7 and 2,3,6-tribromo-4-cyanotoluene. The latter fraction was recrystallized three times from isopropyl ether to give 7 in 29% yield, which was subjected to the Rosenmund-von Brawn reaction to give 8 in 1990 yield. This reaction was carried out under various experimental conditions such as reaction time, reaction temperature, and amount of copper(1) cyanide, but the yield of 8 unfortunately could not be beyond 20%. Instead of 6 , 2 underwent the bromination in the presence of Lewis acid to give 3-bromo-4-ethylbenzonitrile, 2,5-dibromo-4-ethylbenzonitrile, 2,3,5-tribromo-4and ethylbenzonitrile. The intended compound, 3,5-dibromo-4-ethylbenzonitrile, could not be obtained. According to the method of Mao and B~ekelheide,’~ 8 underwent the methylation to obtain 9 in 54% yield. Free radical bromination of 9 gave 10 in 45% yield. It was found that this bromination of 9 (45% yield for the reaction time of 12 days) takes place much more reluctantly compared to that of 4 (67.5% yield for the reaction time of 1 day), probably due to serious steric hindrance effect of two ortho cyano groups. Dehydrobromination of 10 was carried out in a process similar to DCS. When it was performed under the same conditions as DCS (for 8 h), 10 reacted nearly quantitatively but monomeric TCS was barely obtained in 5% yield. The polymer of TCS with the molecular weight of 2500 (by GPC) was produced abundantly, probably suggesting that anionic polymerization of TCS can be induced [MI,’ mg yH3 Brz AlClg Solvent: dichloromethane containing tetrabutylammonium perchlorate (0.1 mol/L). Reference electrode: Ag/AgLc. Relative error: hO.01 V. Calculated by using the equation EA = -EI,Z + 3.09 V.90 run fH3 CN CN 9 TCS 10 with triethylamine. When the reaction time was reduced to 5 h, about a half amount of 10 remained unreacted and polymer of TCS had not yet formed at that time. Therefore, the reaction product in about a half extent of reaction was chromatographed with a silica gel column using isopropyl ether as eluent to separate monomeric TCS and unreacted 10. The overall yield of TCS was barely 0.15%. Electron-AcceptingCharacter of DCS, TCS, DCB, and TCB. First reduction potential, E,, for DCS, TCS, DCB, and TCB and their electron affinity values, EA, are summarized in Table I. TCS and TCB were found to be more electron accepting than DCS and DCB, respectively, the electron-accepting character apparently depending on the number of cyano groups. TCS and DCS are more electron accepting than TCB and DCB, respectively, implying an electron-withdrawing character of the vinyl group even though its Hammett’s substituent or Taft’s polar substituent constant, cr*, has not been reported yet. This character is reasonably assumed also by comparing the Taft’s substituent constants between 1-propenyl (a* = 0.360)18and n-propyl groups (a* = -0.15).18 Polymerization of DCS and TCS. It was found that DCS and TCS are polymerizable with initiators, AIBN, butyllithium, and triethylamine, as summarized in Table 11. Their polymers were obtained as white powder. The polymer of DCS is soluble in acetonitrile, acetone, and DMF and insoluble in benzene, chloroform, ethyl acetate, methanol, and THF. The polymer of TCS also exhibits a similar solubility behavior except for THF, in which it is soluble. In IR measurements, DCS and TCS exhibit an absorption at 1595 cm-l due to the stretching vibration of the carbon-carbon double bond and their polymers do not. In ‘H NMR spectra, DCS and TCS show the peaks in the region 6 6.0-7.3 assigned to the protons of vinyl group and their polymers have a broad absorption in the region 6 2.7-2.0 due to methylene and methine protons. It is Table I1 Polymerizations of 2,4-Dicyanostyrene (DCS) and 2,4,6-Tricyanostyrene(TCS) [IIb [M]/[I] solvent, mL temp, “C time, h conv, 5 ’% qlp/C,C dL/g DCS AIBN 128 CHSCN, 8 60 24 55.7 0.31 BuLi 0 24 4.2 01 . 12 toluene, 5 Et3N 10 toluene, 5 0 24 2.5 0.1 TCS 4 5 6 45.7 25.1 30.4 AIBN BuLi EtSN 42 12 10 benzene, 1 toluene, 4 toluene, 5 60 0 0 17 20 24 57.3 18 . 1.5 1.03 0.1 0.1 OMonomer feed. *Initiator. ‘The solution viscosity was measured with acetone as solvent at 30 O C . dDetermined by GPC with THF as eluent. Macromolecules, Vol. 22, No. 1, 1989 42 Iwatsuki et al. Table 111 Copolymerizations" of 2,4-Dicyanostyrene (DCS) and 2,4,6-Tricyanostyrene (TCS) with Styrene (St) in Acetonitrile at 60 "C copolymer and its composition monomer feed elem anal. comonomer, St, comonomer, comonomer, qsp/C,b run mg mg mol % time, h conv, % H, % C, % N, % mol % dL/g Mn/104c DCS Comonomer 1 76.9 480.0 9.75 2.0 9.61 5.40 84.08 10.52 48.3 2 100.0 272.7 19.9 2.0 11.0 5.78 82.53 11.34 52.9 0.22 133.5 24.9 3 65.4 3.0 10.8 5.63 82.60 11.77 55.4 4 136.9 221.8 29.4 1.8 9.79 5.27 82.04 12.69 61.0 0.22 5 150.0 154.5 39.6 3.0 19.4 5.08 81.73 13.19 64.2 6 143.0 117.3 42.5 1.8 12.6 4.99 80.99 14.13 70.3 0.24 7 189.0 86.3 59.7 1.5 10.3 4.89 79.59 15.51 79.8 62.9 71.7 1.3 8.07 8 235.6 4.81 79.16 16.03 83.5 9 10 11 12 Downloaded by HENKEL KGAA on August 18, 2009 Published on January 1, 1989 on http://pubs.acs.org | doi: 10.1021/ma00191a008 13 53.6 54.8 87.9 109.4 145.7 308.3 141.3 83.6 72.7 54.2 9.2 18.4 37.9 46.7 61.0 4.0 2.5 4.0 7.0 8.0 TCS Comonomer 1.0 5.12 5.6 4.80 16.7 4.19 6.0 4.57 7.3 4.95 81.92 81.48 81.03 80.87 80.29 12.96 13.72 14.78 14.56 14.76 1.03 5.2 6.0 2.3 2.5 41.8 45.0 49.8 48.8 50.0 a Initiator, AIBN 0.5 mol % to total monomer amount; acetonitrile as solvent, 5 mL for the DCS-St system and 3 mL for the TCS-St system. bThe solution viscosity was measured by using THF as solvent at 30 "C. CDeterminedby GPC with THF as eluent. concluded, therefore, that DCS and TCS polymerize through a conventional vinyl polymerization. According to a well-known Tsuruta's classifi~ation'~ of monomers and initiators in anionic polymerization, DCS and TCS are considered to be members of the class of the most susceptible monomers, i.e., nitroethylene, methyl a-cyanoacrylate, vinylidene cyanide, etc., because they are polymerizable with a weak base such as triethylamine. Many attempts to polymerize TNS with radical and other initiators failed' but TNS was spontaneously copolymerized alternatingly with 2- and 4-vinylpyridines (2VP and 4VP) and DMASt.2 Its anionic polymerization, with tertiary amines only, such as triethylamine and vinylpyridines, took place su~cessfully.~ The lack of the polymerizability with radical initiator for TNS was proposed to be associated with the facts that 1,3,5-trinitrobenzene is an efficient retarder or inhibitor of vinyl radical polymerization20and that the retarding effect of aromatic nitro compounds is related to the number of nitro groups.21p22The anionic polymerizability of TNS with tertiary amines such as triethylamine and pyridine3relates to the fact that TNS is electron accepting enough to interact with those weak bases. It was reported that TFS is not polymerizable with a radical i n i t i a t ~ r while 2,5-, 3,5-, and 3,4-bis(trifluoro,~ methy1)styrenes are polymeri~able.~ was suggested that It the lack of the polymerizability for TFS arises from steric hindrance by two ortho trifluoromethyl group^.^ Taft's steric substituent constants, E,, of trifluoromethyl, nitro, and cyano groups are reported23 to be -2.4, -1.01, and -0.50, respectively. The trifluoromethyl group with the lowest value exhibits a steric hindrance effect which is sufficient to prevent polymerization, while the cyano group with the highest value has too small an effect to prevent polymerization. With regard to TNS, the steric effect cannot be discussed at the moment because TNS is polymerizable only with weak bases such as triethylamine and pyridine3 but not polymerizable with other strong base' such as sodium alkoxide and also radical initiat0rs.l Copolymerizationsof DCS and TCS with St. Table I11 summarizes the results of the copolymerizations of DCS and TCS with St and Figure 1 shows their composition diagram. These results were calculated according to the i n t e r ~ e c t i o n ~ ~ the Kelen-Tudos methods25to obtain and the monomer reactivity ratios rl(DCS) = 1.85 f 0.3 and r2(St) = 0.08 f 0.03 at 60 "C for the copolymerization of I 0 ' 0 50 D C S or 100 T C S mol% in f e e d Figure 1. Composition diagrams for the copolymerization of the 0, DCS-St ( 1TCS-St (a),and DCS-DMASt (A) systems in acetonitrile at 60 "C. DCS with St and r,(TCS) = 0.02 f 0.02 and r2(St) = 0.04 f 0.01 at 60 "C for the copolymerization of TCS with St. Alfrey-Price's Q and e values of the DCS and TCS were determined by using these values to be Q = 4.10 and e = +0.58 for DCS and Q = 2.83 and e = +1.86 for TCS, indicating that both DCS and TCS are highly conjugative as well as electron accepting. The copolymerization of p-cyanostyrene (MCS) with St in the presence of benzoyl peroxide at 60 "C in bulk was reported to give its monomer reactivity ratios, rl(MCS) = 1.16 f 0.13 and r2(St) = 0.28 f 0.025.26 The products, r1r2,of the monomer reactivity ratios for the copolymerizations of MCS, DCS, and TCS with St are 0.325, 0.148, and 0.0008, respectively. Thus, the alternating tendency of these copolymerizations increases in the order of MCS, DCS, and TCS, corresponding well to an electron-accepting character of these cyanosubstituted styrenes, the more cyano groups the more electron accepting. Copolymerizations of DCS and TCS with DMASt. Spontaneous copolymerization of TNS with 4VP was found by Yang and Gaoni2 and Butler and Sivaramakrishnan3 even though the polymerization mechanism appears to remain still somewhat equivocal. It was expected on the analogy between nitro and cyano groups that DCS and TCS would be able to polymerize spontaneously with an electron-donating monomer. In this work, DMASt (e = -1.37)n was employed as an electron-donating monomer Preparation and Polymerization of DCS and TCS 43 Macromolecules, Vol. 22, No. 1, 1989 Fraction I Yield: 56 mg IR(NaC1): v(CN) 2240, wlc=c) 1595 H NMR(CDC13): 68.1, 7.4-5.0, 2.9 ' Isopropyl ether insoluble part THF 5 mL Methanol 100 mL .LI Methanol soluble part Methanol insoluble part Downloaded by HENKEL KGAA on August 18, 2009 Published on January 1, 1989 on http://pubs.acs.org | doi: 10.1021/ma00191a008 THF 10 m L Fraction I 1 Yield: 4.5 mg IRlKBr): v(LN) 2240 H NMR (CDC13): 67.9, 2.9 ' Anal. Found: H, 2.93; C , 74.01; N , 23.58 GPC : Methanol 100 mL 1100 \ u 520 1 7 0 0 Mn V Methanol soluble part Methanol insoluble part Fractipn 111 Yield: 13.3 mg IRlKBr) :v!Cb') 2240 H NMR(CDC13): 67.8, 6.3, 2.9, 1.5 ' Anal. Found: H, 5.50; C, 77.18; N, 17.33 GPC: 2700 - Fraction IV Yield: 8.1 mg, H NMRICDCl3): 6 ' Anal. Found: H, N, GPC: IR(KBr): u (CN) nd* 6.3, 2 . 9 , 1.9 8.81; C , 81.48; 9.62 18000 nd = not 7600 2000 6700 28000 M, 14000- 28000 Mn Figure 2. Fractionation scheme of the reaction product between TCS and DMASt and their characterizations. because it is much more electron donating than St and 4VP (e = -0.28).27 When the DCS was mixed with DMASt in acetonitrile, a pale yellow color developed and no further reaction took place. When a radical initiator was added, their copolymerization took place successfully to obtain the polymer with a molecular weight above fifty thousands. Table IV summarizes the results of the copolymerization of DCS with DMASt. The copolymer is soluble in acetone, acetonitrile, DMF, DMSO, and THF and insoluble in chloroform, ethyl acetate, and methanol. These results were calculated according to the i n t e r ~ e c t i o n ~ ~ the and integrated equation24methods to obtain the monomer reactivity ratios as follows: rl(DCS) = 0.12 f 0.02, r2(DMASt) = 0.03 f 0.02 at 60 "C. The product, r1r2,of the monomer reactivity ratio is as small as 0.0036, attributable to the fact that the electron-donating character of DMASt is much stronger than that of St. When TCS was mixed with DMASt, a red color developed. The mixture was kept at room temperature for 98 h and then it was separated into four fractions, I to IV, by the dissolution-precipitation process (see Experimental Section). Figure 2 shows an outline of the fractionation procedure and some properties of the fractions. For fraction I, its ' NMR spectrum shows three kinds H of sharp peaks 6 8.1 (singlet), 7.4-5.0 (multiplet), and 2.9 (singlet). The first peak is assigned to the phenyl protons of the TCS unit, the second is to protons of vinyl groups of TCS and DMASt units and phenyl protons of the (dimethy1amino)phenyl group of the DMASt unit, and the 44 Iwatsuki et al. Macromolecules, Vol. 22, No. I, 1989 Table IV Copolymerization' of 2,4-Dicyanostyrene (DCS) with p -(Dimethylamino)styrene (DMASt) in Acetonitrile at 60 O C copolymer and its composition monomer feed elem anal. run DCS, mg DMASt, mg DCS, mol % time, h conv, % H, % C, % N, % DCS, mol YO h?n/104b 9.6 2.0 2.3 6.97 79.48 13.55 45.4 1 50.5 452.5 3.5 12.0 6.95 249.5 17.2 75.54 13.51 2 54.4 45.0 6.58 30.2 3.3 17.8 79.46 13.96 3 156.0 344.4 50.0 3.3 22.5 6.79 79.88 14.15 52.4 6.4 207.1 39.1 4 139.2 58.0 3.0 26.0 6.80 81.05 14.15 52.4 8.0 5 166.4 1115.0 Downloaded by HENKEL KGAA on August 18, 2009 Published on January 1, 1989 on http://pubs.acs.org | doi: 10.1021/ma00191a008 "Initiator, AIBN 0.5 mol % to total monomer amount; acetonitrile as solvent, 5 mL. bDetermined by GPC with THF as eluent. third is to methyl protons of the dimethylamino group of the DMASt unit. This spectrum can be composed by superposing individual ones of TCS and DMASt monomers. The IR spectrum shows both absorptions of cyano and vinyl groups. It is conceivable, therefore, that fraction I is a mixture of unreacted TCS and DMASt monomers. For fraction 11, its ' NMR spectrum shows two broad H peaks in the 6 7.9 and 2.9 regions, and it is in good agreement with that of the polymer of TCS with a radical initiator. Its IR spectrum exhibits an absorption at 2240 cm-', assigned to the stretching vibration of cyano group. In elemental analysis, the found values of fraction I1 are in good agreement with the calculated ones for the polymer of TCS (H, 2.81; C, 73.74; N, 23.45). Its GPC chart shows an unimodal peak corresponding to the molecular weight of 1100. It is concluded, therefore, that fraction I1 is composed of an oligomer of TCS with a degree of polymerization, of 6. For fraction IV, its ' NMR spectrum exhibits three H broad peaks in the 6 6.3, 2.85, and 1.9 regions, and its profile appears similar to the corresponding one of the polymer of DMASt with a radical initiator. Its IR spectrum carrys no absorption at 2240 cm-', due to the stretching vibration of cyano group. In elemental analysis, the found values coincide well with the calculated ones for the polymer of DMASt (H, 8.92; C, 81.57; N, 9.51). Its GPC chart has an unimodal peak corresponding to a molecular weight of 18000. It is concluded, therefore, that fraction IV is a polymer of DMASt with of 122. For fraction 111, its ' NMR spectrum shows several H broad peaks in the 6 7.8, 6.3, 2.9, and 1.9 regions. The peaks in the 6 7.8 and 6.3 regions me assigned to respective phenyl protons of TCS and DMASt units. Its IR spectrum has an absorption at 2240 cm-', due to the stretching vibration of the cyano group. In elemental analysis, the found values correspond to the calculated ones either for the copolymer composed of 51 mol % TCS unit and 49 mol % DMASt or for the mixture of polymers of TCS and DMASt with the same unit composition. Its GPC chart exhibits bimodal peaks, corresponding to the molecular weight of 2700 and 7600. It is obvious, therefore, that fraction I11 is an oligomeric material composed of TCS and DMASt units, but detailed information cannot be obtained at the moment as to whether its structure is a real copolymer or a mixture of homopolymers. It can be pointed out that when TCS was mixed with DMASt, spontaneous polymerization took place to give a mixture of polymers of TCS (fraction 11) and DMASt (fraction IV), indicating interestingly that anionic polymerization of TCS and cationic polymerization of DMASt occur at the same time. It was reported by Yang and Gaoni2 and Butler and Sivaramakri~hnan~ when TNS was mixed with 4VP that, or DMASt, spontaneous polymerizations took place to give copolymers composed of both monomer units. It was found out by Stille and C h ~ n g ~that~ ~ vinylidene * l when m, m cyanide was mixed with vinyl ethers, two kinds of polymers of respective monomers were obtained at the same time, and they proposed a reaction mechanism that vinylidene cyanide and vinyl ethers are subjected to charge-transfer complex formation and further electron-transfer reaction to give radical cation and radical anion, the former being able to initiate the cationic polymerization of vinyl ethers and the latter being able to initiate the anionic polymerization of vinylidene cyanide. Although no definite information has been obtained on the structure of fraction 111, composed of both monomer units, it is conceivable that TCS and DMASt simultaneously react via a mechanism similar to that of Stille and Chung to give the mixture of the respective polymers. In summary, TCS is highly polymerizable by radical initiation, different from the related 2,4,6-trisubstituted styrenes, TNS and TFS, and it is able to undergo anionic polymerization with weak base initiator such as triethylamine due to its high electron-accepting character. When it is mixed with DMASt carrying with tertiary amine group, anionic polymerization of TCS and cationic polymerization of DMASt take place at the same time to give the mixture containing the homopolymers of TCS and DMASt. Registry No. 1, 1585-07-5; 2, 25309-65-3; 3, 104614-57-5; 4, 104614-58-6; 5, 104614-59-7; 6, 104-85-8; 7, 116596-20-4; 8, 116596-21-5; 9, 116596-22-6; 10, 116596-23-7; DCS, 104696-83-5; TCS, 116596-24-8;St, 100-42-5; DMASt, 2039-80-7; DCS (homopolymer), 104696-84-6; TCS (homopolymer), 116596-25-9; (DCS)(St) (copolymer), 104696-85-7; (St)(TCS) (copolymer), 116596-26-0;(DMASt)(DCS) (copolymer), 116596-27-1;DMASt (homopolymer), 24936-45-6; 4-BrC8H,COCH3,99-90-1. References and Notes Wiley, R. H.; Behr, L. C. J. Am. Chem. SOC.1950, 72, 1822. 1964,86, 5022. Yang, N. C.; Gaoni, Y. J. Am. Chem. SOC. Butler, G. B.; Sivaramakrishnan,K. L. Polym. Prepr. (Am. Chem. SOC., Diu. Polym. Chem.) 1976, 17(2), 608. 1950, 72,5574. McBee, E. T.; Sanford, R. A. J.Am. Chem. SOC. 1950, McBee, E. T.; Sanford, R. A. J. Am. Chem. SOC. 72,4053. Gordon, A. J.; Rord, R. A. The Chemist's Companion: A Handbook of Practical Data, Techniques, and References; Wiley: New York, 1972; p 146. Hein, D. W. J. Am. Chem. SOC. 1948, 70,1897. Marvel, C. S.; Wiley, R. H.; Smith, N. R. J. Am. Chem. SOC. 1948, 70,1560. Marvel, C. S.; Overberger, C. G . J. Am. Chem. SOC. 1946,67, 2250. Sahay, V.; Subramonium,B. J. Indian Chem. Verma, P. S.; SOC. 1937, 14, 157. This compound with bp 188-189 "C was obtained as a byproduct in photobromination of ethylbenzene, but this procedure was not thought to be preparative. Martin, E. L. Organic Reactions; Wiley: New York, 1942;Vol. 1, p 155. Adams, R.; Noller, C. R. Organic Syntheses; Wiley: New York, 1956; Coll. Vol. 1, p 109. Chem. Tsujimoto, K.; Miyake, K.; Ohashi, M. J. Chem. SOC., Commun. 1976, 386. Compound 2 was obtained in UV photoreaction of terephthalonitrile with triethylamine in acetonitrile in 56% yield but the physical properties were not described. Strassburg, R. W.; Gregg, R. A.; Walling, C. J.Am. Chem. SOC. 1947,69, 2141. Macromolecules 1989, 22, 45-51 Bailey, A. S.; Henn, B. R.; Langdon, J. M. Tetrahedron 1963, 19, 161. Iwatsuki. S.: Itoh. T.: Iwai. T.: Sawada. H. Macromolecules , , i985, 18,' 2126. Mao, Y. I.; Boekelheide, V. J. Org. Chem. 1980, 45, 2746. Tdt, W., Jr. Steric Effects in Organic Chemistry; Newman, M. S.. Ed.: Maruzen: Tokvo. 1956: D 556. Tsuruta, T. Anionic Polymerization (in Japanese); Kagakudojin: Tokyo, 1973; p 12. (20) Frank, R. L.; Adams, C. E. J. Am. Chem. SOC.1946,68,908. 1949,48. (21) Food, S. G. J. Chem. SOC. Schulz, G . V. Makromol. Chem. 1947, I , 94. I , (23) (24) (25) (26) (27) (28) (29) (30) 45 Unger, S. H.; Hansh, C. Progr. Phys. Org. Chem. 1976,12,91. Mayo, F. R.; Lewis, F. M. J. Am. Chem. SOC.1944,66, 1694. Kelen, T.; Tudos, F. J. Macromol. Sci. Chem. 1975, A9, 1. Walling, C.; Briggs, E. R.; Wolfstirn, K. B.; Mayo, F. R. J. Am. Chem. SOC.1948, 70, 15. Young, L. J. Polymer Handbook; Brandrup, J., Immergut, E. H., Eds., Wiley: New York, 1975; Vol. 11, p 387. Stille, J. K.; Chung, D. C. Macromolecules 1975, 8, 114. Stille, J. K.; Chung, D. C. Macromolecules 1975, 8, 83. Chen, E. C. M.; Wentworth, W. E. J. Chem. Phys. 1975,63, 3183. Reaction of a-(Trifluoromethy1)styrene with Anionic Initiators Hiroshi Ito,* Alfred F. Renaldo, and Mitsuru Ueda Downloaded by HENKEL KGAA on August 18, 2009 Published on January 1, 1989 on http://pubs.acs.org | doi: 10.1021/ma00191a008 IBM Research Division, Almaden Research Center, 650 Harry Road, Sun Jose, California 95120-6099. Received March 21, 1988 ABSTRACT: a-(Trifluoromethy1)styrene (Q= 0.43, e = 0.90) does not undergo radical homopolymerization. Anionic polymerization fails to produce appreciable amounts of polymer even in bulk at -78 O C in spite of its high e value. The resistance to anionic polymerization is primarily due to side reactions involving addition-eliminationsequences (S,2') when initiators are nucleophilicenough to add to the @-carbon TFMST. of Weaker anionic initiators such as pyridine and potassium tert-butoxide that effectively induce polymerization of methyl a-(trifluoromethy1)acrylate (Q = 0.74, e = 2.5) do not react with TFMST. Reactions of TFMST with several anionic initiators are described in detail. Introduction Methyl a-(trifluoromethy1)acrylate (MTFMA) is reluctant to undergo radical homopolymerization.'i2 AlfreyPrice Q and e parameters for this fluoromonomer have been determined by Ito et al.3 (Q = 0.74, e = 2.5) based on copolymerization analysis and the "mercury methodn4 and also by Iwatsuki et a1.2 (Q = 0.8, e = 2.9) using the Lussi's method.6 The high e value suggests that MTFMA should facilely undergo anionic polymerization. However, anionic initiators such as n-butyllithium (n-BuLi) or phenylmagnesium bromide (PhMgBr) typically employed for polymerization of methyl methacrylate (MMA) failed to produce high molecular weight polymers in good yield.' A similar anomalous behavior of ethyl a-(trifluoromethy1)acrylate in anionic polymerization has been noted by Narita et al.6 Much weaker initiators such as pyridine'^^ and organic and inorganic salts' successfully polymerize MTFMA to high molecular weight polymers. On the basis of GC/MS analysis of n-BuLi-MTFMA reaction products along with the literature survey, Ito and Schwalm suggested that n-BuLi reacts with the 0-carbon of MTFMA followed by spontaneous elimination of LiF to form CF2=, which then reacts with additional n-BuLi (addition-elimination sequence).' Ueda and Ito extended the investigation of the effect of a-CF3 group on the reactivity of vinyl monomers to a-(trifluoromethy1)styrene (TFMST).6 TFMST fails to undergo radical homopolymerization even in bulk a t low temperatures and does not self-propagate ( F T F ~ = 0) in T copolymerization with styrene (ST).6As is the case with MTFMA mentioned above, the Q and e parameters were determined by combining the copolymerization analysis with the mercury method6 since Q and e values cannot be obtained only from the reactivity ratios when one of the ratios is 0. In spite of the favorable Q (0.43) and e (0.90) parameters and the fact that the mercury method has indicated that TFMST adds to a cyclohexyl radical 1.5 times and 7.5 times faster than MMA and ST, respectively, TFMST does not homopolymerize under radical condi0024-9297/89/2222-0045$01.50/0 Table I Attempted Anionic Polymerization of TFMST at -78 "C THF/TFMST initiation initiator (mol % ) (mL/mL) time (day) mode KO-t-Bu/lO-crown-6 (2.0) 2 0 2 0 0 1 0 5 4 3.6 5 6 a b b a a b b KO-t-Bu)l8-crown-6 (2.0) PhMgBr (2.2) PhMgBr (2.4) EtMgBr (5.0) n-BuLi (1.5) n-BuLi (5.0) 3 7 OMixed a t room temperature and cooled to -78 "C. *Mixed at -78 "C. tions presumably due to the large steric hindrance and very low ceiling temperature. Since TFMST (e = 0.90) is more electron-deficient than MMA (e = 0.40) and as electron-poor as methacrylonitrile ( e = 0.81), we attempted anionic polymerization of TFMST with several initiators, which are discussed in this paper. Reactions of acrylic monomers with anionic initiators are quite complex due to the participation of the ester functionality. Therefore, TFMST should provide a good opportunity to study pathways of the reaction between a-CF,-substituted vinyl monomers with anionic initiators without such complications as in the MTFMA case. Although there have been published several papers on the reaction of a-(fluoroalky1)ethylenes with nucleophiles, systematic studies in relation to anionic polymerization have not been reported. In this paper are discussed primary pathways in the reaction of TFMST with various anionic initiators. Results and Discussion As summarized in Table I, anionic polymerizations of TFMST failed under several conditions despite its low electron density on the @-carbon( e = 0.90). Either bulk anionic polymerizations with a high initiator concentration a t -78 "C or mixing TFMST with anionic initiators at room temperature followed by cooling to -78 "C did not 0 1989 American Chemical Society