Study On The Characteristics Of Living Anionic Polymerization Of Bis(Hydrosilylation)DPE Derivatives

With the development of the discipline of polymer chemistry,the research on polymer synthesis methodology is gradually extended to the precise control of the chain structure.The short-range structure（also known as primary structure）is an important factor that determines the performance of synthetic polymers.Therefore,the precise control of the short-range structure of polymer compounds has become a research focus in the field of polymer chemistry.Living anionic polymerization has many advantages in regulating the molecular weight and its distribution,chemical composition and topology structure.Its application in the synthesis of sequence-controllable polymers has received increasing attention.In addition,the microstructure of the copolymerization unit in the polymer chain also has a crucial influence on the performance of the polymer.Designing and synthesizing polymers with a clear sequence structure and microstructure is an important prerequisite for synthesizing polymers with precise topologies.In this paper,DPE-2SiH,a 1,1’-diphenylethylene（DPE）derivative containing a hydrosilylation functional group was designed and synthesized.Alternating copolymers with different microstructures were synthesized by copolymerization with isoprene（Ip）using living anionic polymerization method,and the precise control of the copolymer sequence structure and microstructure was achieved.The alternating copolymer was used as the backbone chain,and combined with the efficient hydrosilylation reaction,a"centipede-shaped"topological polymer was successfully synthesized,and a controllable number of arms of hydrosilylation functionalized s-SIS was synthesized by a coupling agent,which realized the precise synthesis of polymers with complex topological structure.Below are key research findings:1.A DPE derivative containing two hydrosilylation functional groups,DPE-2SiH,was designed and synthesized,and it was copolymerized with St/Ip by living anionic polymerization.When high reactivity DPE-2SiH copolymerizing with St,kinetic problems will occur across the reaction;when copolymerizing with Ip,it will show lower reactivity,the reactivity ratio of Ip was r_Ip=4.21.In the process of DPE-2SiH and Ip copolymerization,the addition of additives can make the comonomer units grow in an alternating form and have a significant effect on the microstructure of the Ip units in the chain.TMEDA can greatly improve the reactivity of DPE-2SiH,which the reactivity ratio of isoprene was r _Ip=0.65.Gaussian simulation was used to investigate the mechanism that the living species of the copolymer are selective for the microstructure of the Ip unit.The results show that the additive affects the angle between the two benzene rings on the subterminal DPE-2SiH,which makes the"space-limited”living species are selective to the Ip unit microstructure.The use of additives efficiently and conveniently achieves precise control of the sequence structure and microstructure content during the copolymerization of DPE-2SiH and Ip.2.The alternating copolymer of DPE-2SiH and Ip with a clear sequence structure is used as the main chain,and the alkynyl group functionalized polyisoprene（PIp-yne）is used as the branched chains,combined with a highly efficient hydrosilylation reaction to synthesize a"centipede-shaped"topological polymer.The grafting conversion of the obtained"centipede-shaped"polymer reached 91.6%,indicating that the hydrosilylation functional groups on the backbone chains accurately and efficiently reacted with the alkynyl groups on the branched chains.At the same time,the regulation of the backbone chains sequence structure and the branched chains branch sites has further realized the precise control of the"centipede-shaped"polymer topology structure.By means of stepwise feeding and controlling the amount of coupling agent,it is possible to effectively control the number of hydrosilylation functionalized s-SIS arms,and successfully realize the accurate synthesis of star topology polymer.