摘要
将N-异丙基丙烯酰胺(NIPAAm)引入小分子烃为模板的苯乙烯细乳液聚合法制备纳米胶囊的体系.水相引发形成的聚异丙基丙烯酰胺(PNIPAAm)低聚物自由基在聚合温度下(大于其最低临界溶解温度)析出并被苯乙烯细乳液液滴吸附,在热力学推动力和静电斥力的共同作用下,PNIPAAm低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,最终得到纳米胶囊.通过透射电镜观察粒子形态和大小;利用接触角测定仪测定了细乳液液滴的表面张力.考察了NIPAAm用量、油溶性单体/小分子烃比例、交联剂用量及乳化剂和引发剂对的种类对胶囊形态的影响.
The comonomer, N-isopropylacrylamide （NIPAAm）, was introduced in the system for synthesis of nanocapules through styrene miniemulsion polymerization by using low molecular weight hydrocarbon as template. The oligomers of poly（N-isopropylacrylamide） dehydrated and separated from water were adsorbed by the droplets of styrene miniemulsion. Due to the thermodynamic force and electrostatic interaction, the oligomer radicals of PNIPAAm anchoring at the interface of droplets make the interface to be the locus of polymerization. Monomers diffused from the internal part of droplets to supply for further polymerization. The nanocapsules can be obtained through the encapsulation of hydrocarbon by the newly-produced polymers separating at the interface of droplets. The morphologies were observed by TEM. The surface tension of miniemusion was measured by a contact angle determinator. The influences on the morphologies of final product such as the amount of NIPAAm, the ratio of monomer and hydrocarbon, the amount of crosslinking agent and the kinds of emulsifier and initiator pair were studied.The results with different amounts of NIPAAm showed that the homogenous nucleation was induced by the excess amount of NIPAAm which was unfavorable to form nanocapsules. With the increase of oil monomer/ hydrocarbon ratio the amount of solid particles increased because the solubility of the NIPAAm in the droplets increased which resulted in the formation of solid particles. The nanocapsules with stable shells were obtained through introducing an appropriate amount of DVB. The entry of the oligomer radicals into nanocapsules was influenced by the initiator/surfactant pair depending on the protection ability of surfactants, the steric hindrance of the ionic groups of the surfactant or the electrostatic repellence.
出处
《高分子学报》
SCIE
CAS
CSCD
北大核心
2007年第12期1116-1120,共5页
Acta Polymerica Sinica
基金
教育部新世纪优秀人才支持计划(项目号NCET-05-0512)资助项目
关键词
纳米胶囊
N-异丙基丙烯酰胺
界面聚合
交联
Nanocapsules, N-isoapropylacrylamide, Interfacial polymerization, Crosslink
