Phase diagrams of stoichiometric polyelectrolyte-surfactant complexes
Phase diagrams of stoichiometric polyelectrolyte-surfactant complexes
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DOI：
10.1021/ma034352c
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发表时间：
2003-12-16
期刊：
影响因子：
5.5
通讯作者：
Strey, HH
中科院分区：
文献类型：
--
作者：
Leonard, MJ;Strey, HH
用小角X射线散射（SAXS）方法建立了一系列自组装的、化学计量的聚[（丙烯酸酯）-co-丙烯酰胺]-十六烷基三甲基铵（PAAm-CTA（+））复合物在水溶液中的相图。空间群和晶胞尺寸为每个观察到的结构进行了测量，作为盐的类型，离子强度，电荷密度，和施加的渗透压的函数。随着渗透压和电荷密度的增加，在0-1000 atm的渗透压范围内观察到了Pm 3 n立方六方密排圆柱（hCPC）片层相序列。这种进展的结构是伴随着每个阶段内的布拉格间距的伴随减少，这些间距的渗透压依赖性表明表面活性剂组件之间的指数力的存在。典型的晶胞尺寸对于立方相为100-150埃，对于六方相为45-60埃，对于层状相为25-35埃。布拉格间距也被发现增加离子强度增加的每种盐类型的研究，这表明反离子释放是一个主要的驱动力，在组装的聚电解质-表面活性剂复合物。在1 M的离子强度，复合物往往解离成不太有序的结构，大概是由于它们成为非化学计量。
Phase diagrams for a series of self-assembled, stoichiometric poly [(acrylate)-co-acrylamide]-cetyltrimethylammonium (PAAm-CTA(+)) complexes in aqueous environments have been established using small-angle X-ray scattering (SAXS). Space groups and unit cell dimensions for each observed structure were measured as a function of salt type, ionic strength, polyelectrolyte charge density, and applied osmotic pressure. As osmotic pressure and charge density were increased, a phase sequence of Pm3n cubic hexagonally close-packed cylinders (hcpc) lamellar was observed over an osmotic pressure range of 0-1000 atm. This progression of structures was accompanied by a concomitant reduction in the Bragg spacings within each phase, and the osmotic pressure dependence of these spacings indicated the presence of exponential forces between surfactant assemblies. Typical unit cell sizes were on the order of 100-150 A for the cubic phase, 45-60 Angstrom for the hexagonal phase, and 25-35 Angstrom for the lamellar phase. Bragg spacings were also found to increase as ionic strength increased for each salt type studied, indicating that counterion release is a major driving force in the assembly of polyelectrolyte-surfactant complexes. At 1 M ionic strength, the complexes tended to dissociate into less well-ordered structures, presumably due to their becoming nonstoichiometric.