双烯化合物类单体合成支化聚合物的支化结构的研究

分别以二乙烯基苯(DVB)、双甲基丙烯酸二缩三乙二醇酯(tri-EGDMA)和1,6-双马来酰亚胺基正己烷(BMIH)为支化单体,采用原子转移自由基聚合合成支化聚苯乙烯;以先核后臂法合成的星状支化聚苯乙烯为参照对合成的支化聚合物的支化形态进行研究.采用气相色谱(GC)、核磁共振氢谱(1H-NMR)和三检测凝胶渗透色谱(TD-SEC)测定了苯乙烯的转化率,聚合物分子量及其分布,特性黏数和均方回转半径.实验结果表明3个支化聚合反应体系内悬垂双键是逐步消耗的,不存在明显的成核过程.反应前期,以形成带有悬垂双键的初级链和轻度支化聚合物为主,聚合物分子量随单体转化率逐步上升;反应后期,悬垂双键聚合导致的分子之间的偶合更加明显,使得聚合物分子量快速上升,合成得到的都是无规支化聚合物.

STUDIES ON THE BRANCHING STRUCTURE OF POLYMERS USING DIVINYL MONOMERS AS THE BRANCHING AGENT

The branched polystyrenes have been prepared via atom transfer radical polymerization(ATRP) using divinylbenzene(DVB),triethylene glycol dimethacrylate(tri-EGDMA) or 1,6-bismaleimidohexane(BMIH) as the branching agent.The four-arm star-shaped polystyrene as the reference was prepared through the way of "core-first" using pentaerythritol tetrakis(α-bromoisobutyrate)(4BrBu) as the initiator,in which,the conversion of styrene was studied using gas chromatography(GC).The consumption of the pendent vinyl group of branched polystyrene was analyzed using proton nuclear magnetic resonance(1H-NMR).The molecular weight,polydispersity index,intrinsic viscosity and mean-square radius of gyration of the branched polymers were measured by triple detection size exclusion chromatography(TD-SEC).The results showed that the pendent vinyl groups of the polymer chains were consumed gradually,and the core formation process was not observed in these polymerization systems of DVB,tri-EGDMA or BMIH.During the early stages of polymerizations,the primary chains with pendent vinyl groups and the slightly branched chains were formed,and the molecular weight of the branched polymer increased gradually with the conversion of styrene.In the later stages,owing to further reaction of the reactive species with the pendent vinyl groups of polymeric chains,the coupling reaction between polymeric chains was more obvious,resulting in sharp increase in the molecular weight of branched polymers.The obtained branched polymers prepared using DVB,tri-EGDMA or BMIH as the branching agents were all randomly branched polystyrene.