疏水缔合两亲高分子的合成与表面活性

Study on the Synthesis and Surface Activities of Hydrophobic Associated Amphiphilic Copolymers

合成了3种含不饱和双键的阳离子型表面活性剂丙烯酸乙酯二甲基(辛基、十二烷基、十六烷基)溴化铵,并对产物进行了结构表征。以此种表面活性剂为疏水单体,丙烯酰胺为亲水单体,在过硫酸铵/亚硫酸氢钠复合引发剂作用下,聚合得到疏水缔合的两亲高分子。采用表面张力仪分别测量了单体表面活性剂和高分子表面活性剂的表面活性。实验结果表明了3种阳离子单体展现了与普通表面活性剂类似的表面性质,而两亲高分子产物具有典型疏水缔合共聚物的聚集行为。对单体阳离子表面活性剂而言,其降低表面张力的效率随疏水碳链的增加而增大,导致临界胶束浓度(cmc)数值下降;而其降低表面张力的效能随链长增加而减弱,这是由于链长增加后发生弯曲,在气液界面上排列更疏松造成的。聚合后的两亲高分子,在低浓度下单链两亲高分子形成分子内胶束,浓度升高疏水长链之间相互缔合形成分子间胶束,因而在表面张力曲线上出现了明显的两个转折点。

Three cationic surfactants containing double bond of acrylate-ethyl dimethyl（ octyl, dodecyl, cetyl）ammonium bromide were synthesized and characterized by IR and UV-Vis spectra. Next,a new type of hydrophobic associated copolymers was synthesized by using these three surfactants as hydrophobic monomers and using acrylamide as a hydrophilic monomer in presence of ammonium persulfate/sodium hydrogen sulfite initiator. The surface activities of the surfactant monomers and the amphiphilic copolymers by the surface tension method were investigated. For three monomer surfactants,the efficiency of reducing surface tension increased with chain length,that is to say,the critical micelle concentrations（ cmc） decreases with increasing of carbon numbers. And,the ability of reducing surface tension,γcmc,decreases with the chain length due to the looser arrangement at air/solution interface because of molecular section area increasing. The surface tension curve of amphiphilic copolymers exhibits two break points,critical aggregation concentration（ cac） and cmc,which indicates that the intramolecular micelles are formed at the low concentration and the intermolecular micelles are formed at higher concentration.