Copolymerization Of Styrene Derivatives With Isoprene By Half-Sandwich Scandium Complex

The copolymerization of styrene and conjugated dienes produced styrene elastomers with different stereo configurations and sequence structures,however,due to the lack of functional groups in these styrene elastomers,the performance and usage of these materials were limited.The research on copolymerization of functional group-containing styrene derivatives and conjugated dienes to produce functionalized styrene elastomers has theoretical and application value for broadening the application field of styrene elastomers.In this thesis,the copolymerization of isoprene with styrene derivatives catalyzed by scandium complex?C₅Me₄SiMe₃?Sc?CH₂C₆H₄NMe₂-o?₂ has been carried out.The effect of substituted groups in styrene derivatives on copolymerization activity and copolymers structure was found.The styrene derivatives-isoprene copolymers with with different compositions and sequence structures have been prepared.1.The copolymerization of isoprene?IP?with p-dimethylsily styrene?St-SiHMe₂?,p-methylthio styrene?St-SMe?and p-chlorostyrene?St-Cl?have been studied.These results showed that the IP-St-SiHMe₂,IP-St-SMe and IP-St-Cl copolymers with controllable IP content?14⁹5 mol%?,high molecular weight?M_n=3.1×10⁴¹6.5×10⁴?and narrow molecular weight distribution?M_w/M_n=1.18².20?were obtained by changing the feed ratio of isoprene to styrene derivatives,in which IP was in 1,4-and 3,4-structure units and the styrene derivatives had a syndiotactic structure.2.The substituents in the styrene derivatives directly affected the copolymerization activities.The copolymerization of St-SiHMe2 and IP was carried out for 6 min in chlorobenzene at room temperature,and the conversion rate of both monomers can be more than 95%.The copolymerization of St-SMe and IP for 60 min under the same polymerization conditions,and the conversion rate of both monomers was more than 86%.The copolymerization of St-Cl and IP for 60 min under the same polymerization conditions,and the conversion rate of IP reached above 96%and St-Cl only 53%.The order of copolymerization of styrene derivatives with IP from high to low was IP/St-SiHMe2>IP/St-SMe>IP/St-Cl.3.The substituents in the styrene derivatives directly affected the sequence structure of the styrene derivative-isoprene copolymers.The obtained IP-St-SiHMe2 copolymers were random copolymers.The IP-St-SiHMe2 copolymers with different compositions have only one glass transition temperature?T_g=12⁸2?C?increasing linearly with the enhance of St-SiHMe₂ content?13⁷9 mol%?.The obtained IP-St-SMe copolymers were multi-block copolymers.The IP-St-SMe copolymers with different compositions have two T_gs(T_g1=-3⁰?C,T_g2=67⁷5?C)originating from the polyIP segment and the polySt-SMe segment and a melting point?T_m=246²50?C?originating from the syndiotactic polySt-SMe segment.The obtained IP-St-Cl copolymers were gradient copolymers.The IP-St-Cl copolymers with different compositions have a T_g?-1⁵?C?originating from polyIP segments and a T_m?314³18?C?originating from syndiotactic polySt-Cl segment.