单茂钪催化乙烯与苯乙烯衍生物共聚合的研究

Copolymerization of Ethylene with Styrene Derivatives Catalyzed by Scandium Complex

以（C5Me4Si Me3）Sc（CH2C6H4NMe2-o）2和[Ph3C][B（C6F5）4]组成的单茂钪催化体系,考察了其催化不同取代基团苯乙烯衍生物均聚合以及与乙烯共聚合的性能.结果表明单茂钪催化体系可以催化对甲基苯乙烯和对乙烯苯基二甲基硅烷均聚合,高活性（106g聚合物（mol Sc）^-1h^-1）地获得高间规聚合物;催化二乙烯基苯和乙烯苯基-1-丁烯聚合会发生不同程度的交联反应.在1.01×10^5Pa乙烯压力下,单茂钪催化体系分别催化对甲基苯乙烯、对乙烯苯基二甲基硅烷与乙烯与共聚合,获得了组成和分子量可控的乙烯/对甲基苯乙烯、乙烯/对乙烯苯基二甲基硅烷共聚物,共聚合活性高达106g聚合物（mol Sc）^-1h^-1.通过1H-NMR、13CNMR、GPC和DSC对共聚物组成、结构和热性能进行了分析表征.结果表明,在1.01×10^5Pa乙烯压力下改变苯乙烯衍生物的用量,共聚物中对甲基苯乙烯或对乙烯苯基二甲基硅烷的摩尔含量可以在8 mol%～55 mol%间调控,共聚物含有间规聚对甲基苯乙烯嵌段或间规聚对乙烯苯基二甲基硅烷嵌段、聚乙烯嵌段和乙烯-苯乙烯衍生物的链接序列,共聚物分子量（Mn）可以在3×10^4～16×10^4间调控,共聚物具有约127℃的熔点.

Syndiospecific homopolymerization of styrene derivatives with different substitution groups such as methyl,methylsilylene,double bond group and their syndiospecific copolymerization with ethylene by halfsandwich scandium complex（C5Me4SiMe3） Sc（CH2C6H4NMe2-o）2in combination with one equivalent of[Ph3C][B（C6F5）4]were examined. In the homopolymerization,the scandium complex displayed high activity（106 g polymer（mol Sc）^-1h^-1） and gave highly syndiotactic poly（p-methylstyrene） and highly syndiotactic poly（p-vinylphenyldimethylsilane） with controlled molecular weight（Mn= 1. 3 ×10^5-5. 7 ×10^5） and narrow molecular weight distribution（Mw/Mn= 1. 48-2. 11）. In the homopolymerizations of divinylbenzene and pvinylphenyl-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 α-methylstyrene under the same conditions,possibly owing to the steric bulkiness of the monomer. More important,by use of this scandium complex,copolymerization of pmethylstyrene and p-vinylphenyldimethylsilane with ethylene under 1. 01 ×10^5 Pa of ethylene has also been achieved with the copolymerization activity reaching up to 106 g polymer（mol Sc）^-1h^-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 using1H-NMR,13C-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（Mn= 3 × 10^4-1. 6 ×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 pvinylphenyldimethylsilane/ethylene with different composition exhibited a melting temperature at about127 ℃,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 ℃,originated from syndiotactic poly（p-methylstyrene） blocks.