PVA-g-PS复合微球的制备与粒径控制研究

Preparation and size control of poly(vinyl alcohol) grafted polystyrene microspheres

由链转移自由基聚合与端基置换反应法,合成了苯乙稀基单封端的聚醋酸乙烯酯(PVAc)大分子单体,使其与苯乙烯在乙醇/水的混合介质中进行自由基分散共聚,得到了表面以PVAc为接枝链的聚苯乙烯(PVAc-g-PSt)微球。将所得微球在碱性条件下醇解,形成了以亲水性聚乙烯醇(PVA)为壳、聚苯乙烯为核的复合微球(PVAc-g-PSt)。用核磁共振对聚合物的结构进行表征,定出了PVAc末端双键的含量;并用激光光散射、扫描电子显微镜对微球的粒径与形态进行了表征。研究结果表明,在共聚反应体系中大分子单体的分子量与浓度、苯乙烯浓度、引发剂浓度及溶剂的组成对微球的形态和粒径大小有明显影响。

Poly（vinyl alcohol）（PVAc） macromononer with a vinylbenzyl end group was synthesized by using free radical polymerization in the preseuce of 2-mercaptethanol as chain transfer agent and end capping reaction with p-choromethyl styrene. The properties of macromonomer. such as molecule structure and the content of vinyl group were cheracterized by nuclear magnetic resonance （^1HNMR）. The PVAc macromonomer was selected as reaction stabilizer to prepare core shell polymeric microspheres. The PVAc-g-PSt microspheres were obtained by dispersion copolymerization of styrene（St） with PVAc macromonomer in ethanol-water mixed solvent at 60℃ for 24h. The PVAc branches on surfaces of the PVAc-g-PSt microspheres successfully led to poly（vinyl alcohol） branches by ethanolysis. The morphology and diameter of the microspheres were studied by using scanning eleetron microscopy （SEM） and laser light scattering（LLS）. The result indicated that the reaction parameters such as molecular weight and [PVAc],[Sy],[AIBN]and percentage of water in the ethanol/water could affect the diameter and morphology of the PVAc-g-PSt microspheres.