正、负离子表面活性剂混合体系溶致液晶生成的相行为

研究了烷基(C8,C12,C14)三甲基溴化铵、烷基(C12,C14)溴化吡啶与烷基(C8,C12)硫酸钠混合体系溶致液晶形成的条件与结构的变化.在高浓度的水溶液中，随着正、负离子表面活性剂摩尔比接近于1，液晶结构由六角相过渡为层状相.表面活性剂非极性链长改变，对相行为影响显著，短碳链的正、负离子表面活性剂混合体系，在等摩尔比时，体系为层状液晶或立方液晶为主，夹杂少许沉淀.随碳链增长，两类表面活性剂间的静电吸引效果表现为生成沉淀的摩尔比例范围变宽，沉淀量增多，共存的液晶相减少，甚至消失.若只改变正离子的极性头基，季胺盐比吡啶盐与烷基硫酸盐的作用要强，形成不溶物的混合摩尔比例范围更宽.

Phase Behavior of Lyotropic Liquid Crystal Formation in Mixed Cationic and Anionic Surfactants System

The formation and structural variation of lyotropic liquid crystal in mixed cationic surfactants (alkyl (C8, C12, C14) trimethylamonium bromide, alkyl (C12, C14) pyridinium bromide) and anionic surfactants (sodium alkyl(C8, C12) sulfate ) systems were studied. When the molar ratio of cationic to anionic surfactant was close to 1, the liquid crystal changed from hexangonal structure to lamellar or cubic structure in concentrated aqueous solu- tion. Variation of nonpolar chain lengthes of surfactants has obvious effects on the phase behavior. When both of cationic and anionic surfactants have short carbon chain length at equimolar mixed ratio, a mixture of large amount of lamellar or cubic liquid crystal and small amount of precipitate was obtained. With the carbon chain length in- creasing amount of precipitate increased. The amount of coexisted liquid crystal decreased, and even disappeared as well. The alkyltrimethylamonium interacted with sodium alkylsulfate more intensively than with alkyl pyridini- um. Therefore, the insoluble mixture produced at wider molar ratio of the two surfactants.