环境因素对正负表面活性剂体系相行为的影响

The Influences of Environment Factor on Phase Behavior of Mixed Catanionic Surfactant Systems

在1:1正负离子表面活性剂混合体系(十二烷基硫酸钠/辛基三甲基溴化铵SDS-C8NM3Br;十二烷基硫酸钠/十二烷基三甲基溴化铵,SDS-C12NM3Br)中加入短链脂肪醇(乙醇,正丙醇,正丁醇),正负离子表面活性剂沉淀溶解,出现表面活性剂双水相.上相有液晶存在,下相有囊泡自发形成.折光率数据和电镜结果表明,上相为表面活性剂富集相,下相表面活性剂浓度较低.混合体系中,出现表面活性剂双水相所需短链脂肪醇的体积百分数,随短链脂肪醇的链长增加而降低.温度升高,出现表面活性剂双水相所需短链脂肪醇的体积百分数降低.对SDS/C8NM3Br/H2O体系的研究结果表明,超声处理可使混合体系中沉淀向囊泡转化,与短链脂肪醇的加入后的作用类似.

Short chain fatty alcohol (ethanol, n-propanol, n-butanol) was added into the 1: 1 mixed systems of cationic and anionic surfactants (sodium dodecyl sulfate-octyltrimythylammonium bromide, sodium dodecyl sulfate-dodecyltrimythylammonium bromide). The precipitation of this kind of catanionic surfactants will be dissolved, and an aqueous two-phase will be formed after the addition of short-chained fatty alcohol. The surfactant concentration is bigger in the upper phase, and smaller in the lower phase respectively. The results of TEM and birefringence observation showed that vesicle and liquid crystal spontaneously formed in the lower and upper phase, respectively. The volume ratio of the aqueous two-phase would increase with the decrease of carbon chain of alcohol, and decrease with the increase of temperature. Sonication also promotes the transition from precipitation to vesicle, which is similar to the effect of addition of short chain fatty alcohols.