Copolymerization of Ethylene with Styrene Derivatives Catalyzed by Scandium Complex

Syndiospecific homopolymerization of styrene derivatives with different substitution groups such as methyl, methylsilylene, double bond group and their syndiospecific copolymerization with ethylene by half. sandwich scandium complex ( C5Me4SiMe3 ) Sc ( CH2C6H4NMe2-o )(2) in combination with one equivalent of [Ph3C] [B(C6F5)(4)] were examined. In the homopolymerization, the scandium complex displayed high activity ( 10(6) g polymer (mol Sc)(-1) h(-1) ) and gave highly syndiotactic poly( p-methylstyrene ) and highly syndiotactic poly( p-vinylphenyldimethylsilane ) with controlled molecular weight ( M-n = 1.3 x 10(5) - 5.7 x 10(5) ) and narrow molecular weight distribution ( M-w/M-n = 1.48 - 2.11 ). In the homopolymerizations of divinylbenzene and p- vinylphenyl-1-butene, cross-linking reaction took place at different extent and the corresponding cross-linking or mico-crosslinking polymers with bimodal GPC profile were obtained. The half-sandwich scandium complex showed no activity in the polymerization of alpha-methylstyrene under the same conditions, possibly owing to the steric bulkiness of the monomer. More important, by use of this scandium complex, copolymerization of p-methylstyrene and p-vinylphenyldimethylsilane with ethylene under 1.01 x 10(5) Pa of ethylene has also been achieved with the copolymerization activity reaching up to 10(6) g polymer ( mol Sc )(-1) h(-1) at room temperature. The copolymerization afforded a novel family of functional polyolefins with syndiotactic poly ( styrene derivatives) blocks, controlled molecular weight and narrow molecular weight distribution. Composition, structure and thermal properties of the novel copolymers were studied using H-1-NMR, C-13-NMR and DSC analysis. These functional copolymers were featured by multi. blocks, including syndiotactic poly( p-methylstyrene ) blocks, syndiotactic poly( p-vinylphenyldimethylsilane ) blocks, polyethylene blocks and ethylene. styrene derivatives sequences. Styrene derivatives content ( 8 mol% - 55 mol% ) and molecular weight ( M-n = 3 x 10(4) - 1.6 x 10(5) ) of the copolymers were easily controlled by changing the feed ratio of styrene derivatives and catalyst. The copolymers obtained from p-methylstyrene/ethylene and p-vinylphenyldimethylsilane/ ethylene with different composition exhibited a melting temperature at about 127 degrees C, originated from polyethylene blocks. When p. methylstyrene content in the p-methylstyrene/ethylene copolymers was more than 55 mol%, the copolymers showed a glass transition temperature at 98 degrees C, originated from syndiotactic poly( p-methylstyrene ) blocks.