有无N-异丙基丙烯酰胺制备纳米微胶囊机理的比较

Comparison of Formation Mechanism of Nanocapsules Through Miniemulsion Polymerization in the Presence or Absence of N-Isopropyl Acrylamide

通过研究交联剂对颗粒形态的影响,提出小分子烃的逃逸是导致生成大量小尺寸实心粒子的主要原因,而交联剂的加入在一定程度上能抑制小分子烃的逃逸.将N-异丙基丙烯酰胺单体引入小分子烃为模板的细乳液聚合法制备的纳米微胶囊体系中,水相引发形成的聚N-异丙基丙烯酰胺(PNIPA)齐聚物自由基在聚合温度下(大于最低临界溶液温度)析出并被细乳液液滴吸附,在热力学推动力和静电斥力的共同作用下,PNIPA齐聚物倾向于分布在液滴和水的界面上,使液滴界面成为主要的聚合场所,单体从液滴内部向界面扩散补充消耗的单体,生成的聚合物在液滴界面上析出,包覆小分子烃液滴,最终得到纳米微胶囊.

According to the morphologies of latexes with and without the crosslinking agent, the escape of hydrocarbon which can be suppressed by the introduction of some amounts of crosslinking agent was considered as the main reason to form small solid particles. On the basis of these results, the comonomer, N-isopropyl acrylamide, was introduced in the system for synthesis of nanocapules through miniemulsion polymerization with liquid hydrocarbon as the template. The oligomers of poly （N-isopropyl acrylamide） （PNIPA） which can be dehydrated and separated from aqueous phase at polymerization temperature were adsorbed by the mini-droplets. Due to the thermodynamic force and electrostatic interaction, the oligomer radicals of PNIPA anchoring at the interface of droplets make the interface to be the loci of polymerization. Monomers diffused from the interior of droplets to supply for further polymerization. The nanocapsules can be obtained through the encapsulation of hydrocarbon by the newly-produced polymers separated at the interface of droplets. The mechanisms of formation of nanocapsules in the system with or without NIPA were compared.