Structural Parameters of Lamellar Phases Formed by the Self-Assembly of Dialkyldimethylammonium Bromides in Aqueous Solution

Journal of the Brazilian Chemical Society

Universidade Estadual de Campinas, Campinas, Brazil¹  Loh, Watson¹  Ferreira, Guilherme A.¹ 

关键词:  double-chain cationic surfactants;    lamellar phases;    liquid crystals;    swelling degree;    interdigitation;   

DOI  :  10.5935/0103-5053.20150297

学科分类：化学（综合）

来源: SciELO

【 摘 要 】

Phase behavior of didodecyl and dioctadecydimethylammonium bromide (DDAB and DODAB) in water was studied using X-ray techniques, differential scanning calorimetry and deuterium nuclear magnetic resonance measurements. Both surfactants self-assemble into lamellar liquid crystalline, either Lα (fluid) and Lβ (gel), phases. The gel-to-fluid phase transition temperature (Tm) in DDAB lamellae was found to be higher than that observed for its vesicles, due to the formation of a stabilized gel phase. In addition, the lamellar phases formed by both amphiphiles differ in their swelling degree and bilayer thickness. DODAB in water formed rather thin bilayers, if compared with the length of the tails, suggesting effective chain interdigitation. These bilayers also presented higher swelling degree than those formed by the shorter-chain homologue DDAB. We propose that these structural properties are strongly influenced by the electrostatic repulsive forces acting on the system.

【 授权许可】

Unknown