González-Delgado Antonio M, Pérez-Morales Marta, Giner-Casares Juan J, Muñoz Eulogia, Martín-Romero María T, Camacho Luis
Departamento de Química Física y Termodinamica Aplicada, Universidad de Córdoba, Campus de Rabanales, Ed. Marie Curie, Córdoba, Spain E-14071.
J Phys Chem B. 2009 Oct 8;113(40):13249-56. doi: 10.1021/jp9055158.
In this paper, we study the collapse of a mixed insoluble monolayer formed by a cationic matrix, dioctadecyl-dimethylammonium bromide (DOMA), and a tetra-anionic porphyrin, tetrakis(4-sulfonatophenyl)porphyrin (TSPP), in a molar ratio TSPP/DOMA = 1:4. During the collapse of this system, we visualized the formation of circular domains consisting exclusively of trilayer, although the domains coalescence was not observed. The coexistence of trilayer and monolayer at the final step of the collapse cannot be interpreted exclusively in terms of a thermodynamic phase equilibrium, intervening as an additional factor the anisotropic line tension of the domain. A high line tension implies a high resistance to the domain deformation, and the anisotropy of the line tension implies the lack of coalescence between these domains, which has been experimentally observed by Brewster angle microscopy for us. Under these circumstances, the domains of collapsed material could enclose monolayer regions where the local surface pressure drops thus stopping the collapse process. The collapse of the TSPP/DOMA system is reversible, that is, the return of the three-dimensional material to the monolayer fits into a simple kinetics according to the nucleation-growth-collision theory. As for the collapse, the reverse process is also affected by the line tension of the domains. This paper relates the high line tension and the anisotropic line tension of a given domains with the reversible nature of the collapse process.
在本文中，我们研究了由阳离子基质二辛基二甲基溴化铵（DOMA）和四阴离子卟啉四（4-磺基苯基）卟啉（TSPP）以摩尔比TSPP/DOMA = 1:4形成的混合不溶性单分子层的崩塌。在该体系崩塌过程中，我们观察到仅由三层组成的圆形区域的形成，尽管未观察到区域合并。崩塌最后阶段三层和单层的共存不能仅用热力学相平衡来解释，区域的各向异性线张力作为一个额外因素介入其中。高线张力意味着对区域变形的高抗性，线张力的各向异性意味着这些区域之间缺乏合并，这一点我们已通过布鲁斯特角显微镜实验观察到。在这些情况下，崩塌物质的区域可能包围单层区域，其中局部表面压力下降，从而停止崩塌过程。TSPP/DOMA体系的崩塌是可逆的，也就是说，根据成核 - 生长 - 碰撞理论，三维物质回到单分子层符合一个简单的动力学。至于崩塌，反向过程也受区域线张力的影响。本文将给定区域的高线张力和各向异性线张力与崩塌过程的可逆性质联系起来。
