Liquid Crystalline Phases of the Amphiphilic Ionic Liquid N-Hexadecyl-N-methylpyrrolidinium Bromide Formed in the Ionic Liquid Ethylammonium Nitrate and in Water
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- 作者：Mingwei Zhao ; Yanan Gao ; Liqiang Zheng
- 刊名：Journal of Physical Chemistry B
- 出版年：2010
- 出版时间：September 9, 2010
- 年：2010
- 卷：114
- 期：35
- 页码：11382-11389
- 全文大小：397K
- 年卷期：v.114,no.35(September 9, 2010)
- ISSN：1520-5207
文摘
The phase behavior of a surfactant-like ionic liquid, N-hexadecyl-N-methylpyrrolidinium bromide (C<sub>16sub>MPB), was studied in both water and a room temperature ionic liquid, ethylammonium nitrate (EAN). Polarized optical microscopy (POM) and small-angle X-ray scattering (SAXS) measurements were employed to investigate the phase behavior of the two systems and to determine which lyotropic liquid crystalline (LC) phases were formed. With increasing C<sub>16sub>MPB concentration, an isotropic solution phase, a hexagonal (H<sub>1sub>) phase, and a cubic phase (V<sub>2sub>) are all present in either EAN or H<sub>2sub>O. The structural parameters of the H<sub>1sub> phase were calculated from SAXS patterns, which show the structural changes as a function of the amount of C<sub>16sub>MPB. The rheological results reveal that the H<sub>1sub> phase constructed by C<sub>16sub>MPB in EAN displays a typical Maxwell behavior, whereas the H<sub>1sub> phase formed by C<sub>16sub>MPB in water shows a gel-like behavior, unlike traditional cationic surfactants. POM and differential scanning calorimetry (DSC) results demonstrate that the lyotropic LC phase in EAN has a higher thermal stability than that formed in H<sub>2sub>O, which may be important to extend the applications of the LC phase.