Copolymerization of dienes with neodymium tricarboxylate-based catalysts and cis-polymerization mechanism of dienes

✍ Scribed by Eiichi Kobayashi; Nahoto Hayashi; Sadahito Aoshima; Junji Furukawa

• Publisher: John Wiley and Sons
• Year: 1998
• Tongue: English
• Weight: 195 KB
• Volume: 36
• Category: Article
• ISSN: 0887-624X
• DOI: 10.1002/(sici)1099-0518(199808)36:11<1707::aid-pola3>3.0.co;2-o

✦ Synopsis

It was found that poly(butadiene), poly(isoprene), and poly(2,3-dimethylbutadiene) with high cis-1,4 content were obtained with Nd(OCOR) 3 -(i-Bu) 3 Al-Et 2 AlCl catalysts (R Å CF 3 , CCl 3 , CHCl 2 , CH 2 Cl, CH 3 ) in hexane at 50ЊC [cis-1,4 content: poly(BD), ú 98%; poly(IP), ¢ 96%; poly(DMBD), ¢ 94%]. Copolymerization of IP and styrene (St) was carried out at various monomer feed ratios to evaluate the monomer reactivity ratio and cis-1,4 content of the diene unit and then to elucidate the cis-1,4 polymerization mechanism of IP. The cis-1,4 content of the IP unit in the copolymers decreased with increasing St content in the copolymers. The cis-1,4 polymerization was disturbed by incorporating St unit in the copolymers, since the penultimate St unit hardly coordinates to the neodymium metal, resulting in a decrease of the cis-1,4 content in the copolymers. That is, the cis-1,4 polymerization of IP is suggested to be controlled by a back-biting coordination of the penultimate diene unit. On the other hand, in the case of poly(BD-co-IP) and poly(BD-co-DMBD), the cis-1,4 content of the BD, IP, and DMBD units in the copolymers was almost constant ( cis: 94-98%), irrespective of the monomer feed ratios and polymerization temperature. Consequently, the penultimate IP and DMBD units favorably control the terminal BD, IP, or DMBD unit to the cis-1,4 configuration through the back-biting coordination. For the monomer reactivity ratios, a clear difference was observed in each system: r BD Å 1.22, r IP Å 1.14; r BD Å 40.9, r DMBD Å 0.15. Low polymerizability of DMBD was mainly ascribed to the steric effect of the methyl substituents.