乙醇或乙醇-水为新的溶剂体系沉淀聚合制备单分散聚合物微球

以三羟甲基丙烷三丙烯酸酯(TMPTA)作交联剂,, 苯乙烯 (St) 作共聚单体,, 偶氮二异丁腈(AIBN)作引发剂,, 在低毒性乙醇和乙醇-水混合物这一新的溶剂体系中沉淀聚合反应4 h制备了单分散交联微球. 通过提高交联剂用量、引发剂用量和改变反应介质中水的用量探讨了提高单体转化率的方法. 结果表明,, 提高引发剂用量和增加溶剂中水的用量都能有效提高单体转化率并制得粒径均匀的微球. 保持其他条件不变,, 在乙醇中使用2 wt% AIBN仅能得到79%的单体转化率,, 提高AIBN用量至6 wt%或在介质中增加水的用量至28 vol%,, 在制得单分散微球的同时单体转化率可以达到95%以上. 文中对微球的形成机理和提高单体转化率的方法给出了理论解释.

Preparation of Polymer Uniform Microspheres via Precipitation Polymerization in Ethanol or Ethanol-Water water Mixture as New Solvent

Uniform microspheres were prepared through precipitation polymerization of 1,1,1-tris(hydro- xymethyl) propane triacrylate (TMPTA)-Styrene styrene (St) with azobisisobutyronitrile (AIBN) as initiator in ethanol and ethanol-water mixture, new solvent systems with low toxicity. Impacts of TMPTA amounts, initiator concentrations and water content in the solvent mixture were studied. Uniform microspheres were obtained within 4 h along with higher monomer conversion. Results demonstrated clearly that increase of initiator amounts and use of water as a cosolvent were indeed very effective to promote the polymerization to high conversions and to get uniform microspheres. With no water under otherwise the same experimental conditions, only about 79% of monomer conversion was detected; while monomer conversion was remarkably increased to 95% when 28 vol% of water was added into ethanol. To reach to this high conversion with no water in the medium, 6 wt% of AIBN was needed. Mechanisms of microsphere formation and methods to promote monomer conversion were also explained.