Pocivavsek Luka, Frey Shelli L, Krishan Kapilanjan, Gavrilov Kseniya, Ruchala Piotr, Waring Alan J, Walther Frans J, Dennin Michael, Witten Thomas A, Lee Ka Yee C
Department of Chemistry, Institute for Biophysical Dynamics, James Franck Institute, University of Chicago, Chicago, IL, USA. E-mail:
Soft Matter. 2008 Jan 1;4:2019-2029. doi: 10.1039/b804611e.
Surfactants at air/water interfaces are often subjected to mechanical stresses as the interfaces they occupy are reduced in area. The most well characterized forms of stress relaxation in these systems are first order phase transitions from lower density to higher density phases. Here we study stress relaxation in lipid monolayers that occurs once chemical phase transitions have been exhausted. At these highly compressed states, the monolayer undergoes global mechanical relaxations termed collapse. By studying four different types of monolayers, we determine that collapse modes are most closely linked to in-plane rigidity. We characterize the rigidity of the monolayer by analyzing in-plane morphology on numerous length scales. More rigid monolayers collapse out-of-plane via a hard elastic mode similar to an elastic membrane, while softer monolayers relax in-plane by shearing.
空气/水界面处的表面活性剂常常会受到机械应力，因为它们所占据的界面面积会减小。在这些体系中，最具特征的应力松弛形式是从低密度相到高密度相的一级相变。在此，我们研究了脂质单分子层在化学相变耗尽后发生的应力松弛。在这些高度压缩的状态下，单分子层会经历称为塌陷的整体机械松弛。通过研究四种不同类型的单分子层，我们确定塌陷模式与面内刚性最为密切相关。我们通过在多个长度尺度上分析面内形态来表征单分子层的刚性。刚性更强的单分子层通过类似于弹性膜的硬弹性模式发生面外塌陷，而较软的单分子层则通过剪切在面内松弛。
