二维压缩系数研究二十二酸Langmuir膜的相态转变特征

本文采用二维压缩系数研究了二十二酸Langmuir膜的相态转变特征。通过相态转变前后压缩系数的变化特点，发现二十二酸单分子膜存在两种相变类型。第一类是当相变从L2态到L2’态时，压缩系数曲线出现一个峰值，然而相变前后的压缩系数不变，bi=bf。第二类是当相变从L2’态到S态时，压缩系数陡降，压缩系数曲线出现一个台阶。第一类相变可能的机理是在缓慢压缩过程中分子有自发性的重新排列过程，而第二类相变则是主要依赖于外力的持续压缩，被动性的分子自组装过程，bi>bf。

New Features on the Phase Transitions of Behenic Acid Monolayers as Unveiled by 2D‐Compressibility Coefficient

Phase behavior of Langmuir monolayers of behenic acid (BeA) has been examined by two‐dimensional compressibility. It was found that phase transitions of BeA could be classified into two distinct categories, named Type‐I and Type‐II in this work. The former is typified by a positive peak on the compressibility‐pressure (β‐) curve, indicating the transition can occur itself in a way of collapse from the initial structure. The latter is characterized by a dropping step on the β‐ curve, implying that it cannot happen itself and the driven force is continuous compression. For BeA molecules, compressibility coefficients at the initial and final state are the same, β_i=β_f, for Type‐I phase transition from L₂ to L₂' state, whilst β_i>β_f for Type‐II phase transition from L₂' state to S state.