Mass density measurements as a tool to distinguish between micelle size and shape in nematic and chiral nematic phases
作者:M. Acımış、E. Akpınar
DOI:10.1039/b304693a
日期:——
The relative alteration in micelle size and micelle shape brought about by two sets of specific solutes have been investigated by mass density measurements at constant composition and temperature. The mass density of the first set of solutes, phenol, benzene, cyclohexanol and cyclohexane, was measured in the same host phase and found to change in the order: phenol > cyclohexanol > benzene > cyclohexane. The contribution of the solutes to the mass density of the host phase was interpreted to arise from the capability of the hydrophilic group and the hydrophobic part of the solutes to interact with the corresponding region of the host micelle. The second set consisted of racemic amphiphilic mixtures and their enantiomers, decyl- and dodecyl-esters of serine and alanine. It was found that the mass density increases in the serine phases but decreases in the alanine ones as the DL-racemic amphiphiles of the nematic phases were replaced by their L-isomers. These phenomena were shown to arise from a definite arrangement of the head groups in the racemic nematic and intrinsic chiral nematic phases. Furthermore, on the basis of the mass density difference between the achiral/induced chiral nematics and the racemic/intrinsic chiral nematics, a distinction between the induced chiral nematic phases and the intrinsic chiral ones is possible.
常组成和温度下,通过质量密度测量研究了两组特定溶质对胶束大小和胶束形状的相对改变。第一组溶质:苯酚、苯、环己醇和环己烷,在相同主相中测得的质量密度变化顺序为:苯酚 > 环己醇 > 苯 > 环己烷。溶质对主相质量密度的贡献被解释为溶质的亲水基团和疏水部分与主相胶束相应区域相互作用的能力。第二组是由外消旋两性混合物及其对映体组成:丝氨酸和丙氨酸的癸酯和十二酯。研究发现,当向列相的外消旋两性取代为其L-异构体时,丝氨酸相的质量密度增加,而丙氨酸相的质量密度减小。这些现象被证明是由外消旋向列相和固有手性向列相中头部基团的特定排列引起的。此外,根据非手性/诱导手性向列相与外消旋/固有手性向列相之间的质量密度差异,可以区分诱导手性向列相和固有手性向列相。