Studies on Association-dissociation and Interaction of Hydrophilic, Reversible Colloids

点击翻译按钮获取中文摘要

Our investigation on the salt-induced sphere-rod transition of micelles of ionic surfactants has been extended to aqueous sodium halide soultions of alkyltrimethylammonium halides having teragecyl and cetyl groups, Halides are chloride and bromide. Micelle molecular weight was been measured by light scattering. The threshold salt concentration of the sphere-rod transition is lower, as the alkyl chain is longer and as the counterion is bromide rather than chloride. The dependence of micelle molecular weight of rodlike micelles on the salt concentration is primarily determined by the degree of counterion binding. Ultracentrifugal sedimentation of aqueous NaCl solutions of dodecyldimethylammonium chloride has been measured, and charateristic feature is observed on the schlieren pattern of rodlike micelles, accompanying spherical micelles, and having strong concentration dependence of sedimentation coefficient itself. Solubilization power toward a water-insoluble dye is about twice larger for rodlike micelles than for spherical micelles.Light scattering from aqueous solutions of dimethyloleylamine oxide in the presence of HCl or NaCl or both has been measured, and anomalous angular dependence is observed, indicating strong external interference, when the rodlike micelle has molecular weight around a million.The effects of cationic surfactants on the conformation of anionic polypeptides, i.e.,sodium poly-L-glutamate and sodium poly-S-carboxymethyl-L-cyteine, have been examined by means of ciruclar dichroism measurements. Dodecylammonium chloride can induce the -helix and the -conformation, respectively, in aqueous solution, but its N-methyl-substitution reduces this induction. Generally, alkylammonium chlorides having alkyl longer than heptyl can induce the -helix of poly-L-glutamic acid, but their effects inducing the -conformation of poly-S-carboxymethyl-L-cysteine are somewhat compli-cated.