辐射冷冻乳液聚合制备多孔聚合物微球

Preparation of multi-hollow polystyrene microspheres by radiationinduced frozen emulsion polymerization

本文研究了常规苯乙烯乳液和苯乙烯细乳液在两种不同冷冻条件下,即液氮冷冻和-20℃冰箱冷冻过程中乳液体系稳定性的变化,以及γ射线辐射引发冷冻乳液中单体聚合得到的聚苯乙烯微球的形貌,并探讨了形貌形成机制.结果表明,乳液在-20℃冰箱中冷冻过程中乳液稳定性破坏,单体出现分层现象.而液氮冷冻可以保持冷冻前的乳液相态结构.γ射线辐射可以引发冻乳液中苯乙烯聚合,聚合过程中体系经历了从O/W乳液向W/O/W多重乳液的转变,最终形成粒径分布较宽,直径为1~20μm的泡孔状多孔PS微球.本工作不仅为低温聚合技术提供了新思路,也为多孔聚合物微球材料的制备提供了新方法.

In this article, the stability of a classic emulsion and a mini-emulsion composed of water, styrene （St） and sodium dodecyl sulfate （SDS） during the freezing process in liquid nitrogen and refrigerator （-20 ℃） respectively was studied. Creaming appeared in the classic emulsion and mini-emulsion during the freezing process in refrigerator, however, no lamination was observed in any emulsions during their freezing process in liquid nitrogen. The polymerization of St monomer in frozen emulsions by liquid nitrogen freezing was then initiated by γ-ray radiation at -5℃. The inner phase structure of both frozen classic emulsion and mini-emulsion would experience a change from an O/W emulsion to a W/O/W multiple emulsion during the polymerization process, and finally, multi-hollow polystyrene microspheres with a diameter of about 1-20 μm were fabricated. This article provides not only a new idea to develop the low-temperature polymerization technique, but also a simple and green new method to prepare porous polymeric microspheres.