Critical Temperature and LE/G Phase Transitions in Monolayer Films of the Amphiphilic TEMPO Derivatives at the Air/Water Interface
作者:Michael J. Johnson、Chinmay Majmudar、Janusz J. Skolimowski、Marcin Majda
DOI:10.1021/jp0122878
日期:2001.9.1
Phase behavior of five members of a homologous series of 4-alkaneamido-2,2,6,6-tetramethyl-1-piperidinyloxy (CnTEMPO with n = 14, 16, 18, 20, 22) was investigated with classical Langmuir monolayer techniques and with Brewster angle microscopy and 2D voltammetry. Surface potential data, BAM images, and 2D voltammetry showed that only C20- and C22TEMPO monolayers have a 2D LE/G critical point above room
用经典的 Langmuir 单层技术研究了同源系列 4-alkaneamido-2,2,6,6-tetramethyl-1-piperidinyloxy (CnTEMPO,n = 14, 16, 18, 20, 22) 的五个成员的相行为和布鲁斯特角显微镜和二维伏安法。表面电位数据、BAM 图像和 2D 伏安法表明,只有 C20- 和 C22TEMPO 单分子层具有高于室温的 2D LE/G 临界点,其余三种具有较短烷烃链的化合物形成超临界单分子层。这些两亲物的临界温度异常低的原因是它们的头基的分子结构具有两个极性基团(硝基氧基和酰胺基团),这些极性基团位于庞大的哌啶环的相反位置。两个极性基团的存在导致单层膨胀过程中头基的方向发生变化,并导致这些两亲物的横截面积显着增加(约 50-100 A2/分子)。因此...