苯乙烯-间戊二烯-对甲基苯乙烯阴离子共聚合

Anionic Copolymerization of Styrene,1,3-Pentadiene and p-Methyl-Styrene

间戊二烯单体与苯乙烯可以通过阴离子共聚合实现特殊交替序列结构共聚物,此类材料在高抗冲击性树脂和增韧材料方面有特殊用途。本文利用苯乙烯(ST)、间戊二烯(PD)和对甲基苯乙烯(MST)的阴离子共聚合方法,通过“一步法”制备了新型序列共聚物,并对聚合动力学及共聚物微观序列结构进行了系统研究。研究表明:均聚单体活性ST>MST>>PD,聚合反应动力学级数n=1,单体均可以定量转化;^(1)H-NMR在线分析表明,PD/ST和PD/MST共聚单体等摩尔消耗,结合竞聚率数据推测PD倾向与苯乙烯类单体均可形成交替结构,且PD主要是1,4-加成方式嵌入主链;三元共聚活性可控程度极佳,相对分子质量与转化率成良好的线性关系,分子量分布低于1.10;三元共聚物中间戊二烯组成(FPD=0.5)似乎与转化率无关,但ST和MST共聚单体含量均与转化率成线性关系;基于PD独特的二元交替共聚行为,推测了可能共聚合机理。

1,3-Pentadiene can undergo anionic copolymerization with styrene derivatives to give special alternating sequence-controlled copolymers,which have significantly applications in the area of impact resistance of resins and toughening agents.In this article,a series of copolymers were obtained via anionic copolymerization using styrene(ST),1,3-pentadiene(PD)and p-methyl-styrene(MST)as monomers and n-BuLi as initiator.The copolymerization kinetics analysis as well as the microstructure of copolymers was investigated in detail and some results show that:(1)the hopolymerization activities order is ST>MST>>PD and all polymerization kinetics analysis all show the evolution of-ln(1-x)versus t is strictly linear,and the copolymer yield easily reaches up to 100%;(2)the real-time NMR analysis show the composition of PD in poly(PD-alt-ST)or poly(PD-alt-MST)is constant(F_(PD)=50%),and the NMR spectra results together with the reactivity ratio data all prove the alternating sequence microstructure.Moreover,the PD monomer has priority to undergo 1,4-addition reaction to give the predominant 1,4-units;(3)the alternating copolymerization and terpolymerization proceed in a living and controlled manner,and the molecular weight is well agreement with the theoretical value,also the molecular weight distribution is lower than 1.10;(4)in the case of n(MST)/n(ST)/n(PD)=1/1/2 system,the composition of PD in terpolymer is constant(FPD=0.5)and the evolution of styrene composition(FST or FMST)versus x is strictly linear;(5)based on the dual-alternating copolymerization strategy of PD,the possible alternating polymerization mechanism was proposed.