Properties of Dilute Aqueous Solutions of Double-Chain Surfactants, Alkyldodecyldimethylammonium Bromides with a Change in the Length of the Alkyl Chains
作者:Koichi Hiramatsu、Keiichi Kameyama、Ryo Ishiguro、Masaki Mori、Hisao Hayase
DOI:10.1246/bcsj.76.1903
日期:2003.10
A series of cationic surfactants, dialkyldimethylammonium bromides with dodecyl as the primary alkyl chain and with methyl, ethyl, propyl, butyl, hexyl, octyl, and decyl as the second alkyl chain, as well as those with symmetric alkyl chains, dioctyl, didecyl and didodecyl ones, were synthesized, and their properties were investigated through measurements of the conductivity and air–liquid surface tension for their aqueous solutions to determine their critical micelle concentrations (cmc) and surface adsorption parameters in the formulation according to a two-dimensional lattice model in the form of the Frumkin equation. The change in cmc revealed that the free energy to transfer from water to the micelle per methylene unit is significantly small for asymmetric double-chain surfactants with a shorter second alkyl chain, and it approaches as elongating the second alkyl to those for the single-chain and symmetric double-chain surfactants. The free energy to transfer to an air–solution interface decreased approximately linearly with the total length of the hydrocarbon chains for all of the species examined. The lattice area for a symmetric double-chain surfactant molecule decreased with the length of its hydrocarbons. In a series of asymmetric ones, it showed a maximum for that with hexyl in its second alkyl.
合成了一系列阳离子表面活性剂,即以十二烷基为第一烷基链,以甲基、乙基、丙基、丁基、己基、辛基和癸基为第二烷基链的二烷基二甲基溴化铵,以及以二辛基、二癸基和二十二烷基为对称烷基链的阳离子表面活性剂、并通过测量其水溶液的电导率和气液表面张力来研究它们的性质,从而根据弗鲁姆金方程形式的二维晶格模型确定它们在配方中的临界胶束浓度(cmc)和表面吸附参数。cmc 的变化表明,对于第二烷基链较短的不对称双链表面活性剂来说,每个亚甲基单位从水转移到胶束的自由能很小,随着第二烷基的拉长,其自由能接近于单链和对称双链表面活性剂的自由能。对于所研究的所有种类,转移到空气-溶液界面的自由能随着碳氢链总长度的增加而近似线性下降。对称双链表面活性剂分子的晶格面积随着碳氢化合物长度的增加而减小。在一系列不对称分子中,第二个烷基为己基的分子的晶格面积最大。