沉淀聚合制备聚(季戊四醇三丙烯酸酯-苯乙烯)单分散微球及其形成机理

以季戊四醇三丙烯酸酯(PETA)作交联剂,苯乙烯作共聚单体,偶氮二异丁腈作引发剂,在乙醇或其与水的混合溶剂中沉淀聚合制备了交联聚合物微球.研究了反应时间、交联剂用量以及溶剂中水含量对聚合过程及微球的影响.结果表明当PETA用量在单体质量的5%-35%之间且反应时间不低于6h时可制得单分散聚合物微球.当PETA用量低于20%时,所得微球的粒径随PETA用量的增加逐渐减小,粒径分布逐渐变窄;此后继续提高PETA用量,微球粒径又逐渐增大,粒径分布逐渐变宽.向反应介质中加入水,可明显提高微球产率及单体转化率,但其体积分数达30%时,所得微球分散性变宽.在此基础上对微球的形成机理也进行了讨论.

Preparation and Formation Mechanism of Uniform Polymer Microspheres in Precipitation Polymerization of Pentaerythritol Triacrylate and Styrene

Uniform polymer microspheres were prepared through precipitation polymerization of pentaerythritol triacrylate(PETA)and styrene in ethanol or an ethanol-water mixture using azobisisobutyronitrile(AIBN)as initiator.The effects of the polymerization time,amount of PETA,and water content in the mixed solvent on the polymerization process and the microspheres were studied. Uniform microspheres were readily obtained when the amount of PETA was between 5%and 35% (mass fraction)relative to all monomers with a polymerization time of 6h.When the mass fraction of PETA was<20%,the microspheres decreased in size and became more uniform as the PETA mass fraction increased.By contrast,when the PETA mass fraction was>20%,the microspheres size increased and the size distribution became larger as the PETA mass fraction increased.With the ethanol-water binary solvent mixture,the monomer conversion and microsphere yield increased compared with those obtained with pure ethanol.However,the water volume fraction needed to be kept below 30%,above which the uniformity of the microspheres was deteriorated.Based on the results,the mechanism of microsphere formation is discussed.