Effect of headgroups on the aggregation behavior of cationic silicone surfactants in aqueous solution

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• 作者：Jinglin Tan ; Depeng Ma ; Shengyu Feng ; ^{fsy@sdu.edu.cn} ; Changqiao Zhang ; ^{zhangchqiao@sdu.edu.cn}
• 关键词：Cationic silicone surfactants ; Electrical conductivity ; Degree of counterion binding ; Entropy-driven ; Enthalpy-driven
• 刊名：Colloids and Surfaces A: Physicochemical and Engineering Aspects
• 出版年：2013
• 出版时间：20 January, 2013
• 年：2013
• 卷：417
• 期：Complete
• 页码：146-153
• 全文大小：613 K

文摘

Three cationic silicone surfactants, 1-methyl-3-[tri-(trimethylsiloxy)]silylpropyl-imidazolium chloride (Si₄mimCl), (2-hydroxyethyl)-N,N-dimethyl-3-[tri-(trimethylsiloxy)]silylpropylammonium chloride (Si₄mam-OHCl), 1-methyl-1-[tri-(trimethylsiloxy)]silylpropylpyrrolidinium chloride (Si₄pyCl), with the same hydrophobic group and different headgroups were synthesized. Their aggregation behavior in aqueous solution was systematically investigated by surface tension, electrical conductivity, and steady-state fluorescence. Surface tension of water can be reduced almost to 20 mN m^?1 with the addition of the cationic silicone surfactants. This result indicates that all the three surfactants exhibit remarkable surface activity. Because of the effect of the headgroups, the critical micelle concentrations (CMC) values increase following the order Si₄pyCl < Si₄mimCl < Si₄mam-OHCl, and Si₄pyCl packs more tightly at the air/water interface compared with Si₄mimCl and Si₄mam-OHCl. Electrical conductivity measurements show that all the three cationic silicone surfactants have low degree of counterion binding (¦Â) and the ¦Â values for Si₄pyCl and Si₄mam-OHCl increase with increasing the temperature in the investigated temperature range. Thermodynamic parameters (, , and ) of micellization indicate that the micellization for Si₄mimCl in aqueous is enthalpy-driven, and that for both the Si₄pyCl and Si₄mam-OHCl entropy-driven.