Feitosa E, Jansson J, Lindman B
Physics Department, Sao Paulo State University, IBILCE/UNESP, Rua Cristovao Colombo, 2265, Sao Jose do Rio Preto, CEP 15054-000, SP, Brazil.
Chem Phys Lipids. 2006 Jul;142(1-2):128-32. doi: 10.1016/j.chemphyslip.2006.02.001. Epub 2006 Mar 3.
Differential scanning calorimetry (DSC) and dynamic light scattering (DLS) were used to obtain the gel to liquid-crystalline phase transition temperature (Tm) and the apparent hydrodynamic radius (Rh) of spontaneously formed cationic vesicles of dialkyldimethylammonium bromide salts (CnH2n+1)2(CH3)2N+.Br-, with varying chain lengths. The preparation of cationic vesicles from aqueous solution of these surfactants, for n=12, 14, 16 and 18 (DDAB, DTDAB, DHDAB and DODAB, respectively), requires the knowledge of the surfactant gel to liquid-crystalline phase transition temperature, or melting temperature (Tm) since below this temperature these surfactants are poorly or not soluble in water. That series of cationic surfactants has been widely investigated as vesicle-forming surfactants, although C12 and C18, DDAB and DODAB are by far the most investigated from this series. The dependence of Tm of these surfactants on the number n of carbons in the surfactant tails is reported. The Tm obtained by DSC increases non-linearly with n, and the vesicle apparent radius Rh is about the same for DHDAB and DODAB, but much smaller for DDAB.
采用差示扫描量热法（DSC）和动态光散射法（DLS），测定了不同链长的二烷基二甲基溴化铵盐（CnH2n+1）2(CH3)2N+.Br-自发形成的阳离子囊泡的凝胶-液晶相变温度（Tm）和表观流体力学半径（Rh）。由这些表面活性剂（n分别为12、14、16和18，即分别为DDAB、DTDAB、DHDAB和DODAB）的水溶液制备阳离子囊泡，需要了解表面活性剂的凝胶-液晶相变温度或熔点（Tm），因为在此温度以下，这些表面活性剂在水中的溶解性很差或不溶。尽管C12和C18（即DDAB和DODAB）是该系列中研究最多的，但这一系列阳离子表面活性剂作为形成囊泡的表面活性剂已得到广泛研究。本文报道了这些表面活性剂的Tm对表面活性剂尾部碳原子数n的依赖性。通过DSC得到的Tm随n呈非线性增加，DHDAB和DODAB的囊泡表观半径Rh大致相同，但DDAB的要小得多。
