聚苯乙烯/蒙脱土纳米复合材料的制备及结构研究

PREPARATION AND STRUCTURE OF POLYSTYRENE/MONTMORILLONITE NANOCOMPOSITE

以可与苯乙烯发生共聚的阳离子表面活性剂乙烯苄基二甲基十八烷基氯化铵(VOAC)为插层处理剂改性蒙脱土(VC18-MMT),有机蒙脱土在超声波强剪切作用以及乳化剂作用下预分散在乳化剂溶液中,然后引入苯乙烯单体进行原位乳液聚合制备聚苯乙烯/蒙脱土纳米复合材料.采用XRD和TEM对纳米复合材料的结构进行了表征.结果表明,绝大多数的蒙脱土被剥离成单个片层均匀的分散在聚合物基体中;动态力学分析表明,纳米复合材料的储能模量和玻璃化温度均有所增加,而动态损耗有所降低;接枝在蒙脱土片层上的聚合物通过与锂离子进行阳离子交换反应提取下来,采用GPC和NMR对接枝聚合物的结构进行了表征,结果表明,接枝聚合物是较基体分子量低且分布很宽的苯乙烯和乙烯苄基二甲基十八烷基氯化铵的共聚物,计算表明每一个共聚物分子链上平均含有大约25个乙烯苄基二甲基十八烷基氯化铵分子.

The organic montmorillonite VC18-MMT was prepared by the exchanging inorganic cations with vinylbenzyldimethyloctadecylammionun chloride （VOAC） which could be co-polymerized with styrene. The predispersion of VC18-MMT was realized via sonicating the suspension of the montmoriUonite particles in emulsifier solution, and then the styrene was added into the system and the in situ emulsion polymerization was carried out to prepare PS/VC18-MMT nanocomposites. The structure of final nanocomposites was characterized by XRD and TEM. The resuhs indicated that the most of montmorillonite was fully exfoliated into individual layers and uniformly dispersed in the polystyrene matrix. The dynamic mechanical properties of the nanocomposites were determined by DMA, which demonstrated that the storage modulus and glass transition temperature of polystyrene were increased by compositing of montmorillonite. The polymer grafted on the layers of montmorillonite could be obtained by ion exchanging with lithium cations. The structure and average molecular weight of the polymer were characterized by NMR and GPC. The resuhs showed that the polymer grafted on layers of montmoriUonitc was identifed as the copolymer of styrene with VOAC and the average molecular weight of the copolymer was lower than that of free polystyrene. One copolymer chain averagely comprised about 25 VOAC molecules, which can be calculated through the concentration of VOAC and the mass of copolymer in the galleries of montmorillonite.