单一非离子表面活性剂制备胶质气体泡沫的稳定性

用单一的十二烷基醇聚氧乙烯醚(C12EOn)非离子表面活性剂制备了稳定的胶质气体泡沫(CGA). 采用偏光显微镜和流变仪对其表面活性剂溶液相态和泡沫体系的微观结构及流变行为进行研究, 以探索CGA的稳定化机理. 实验结果表明, 分别由C12EO3和C12EO5制备的CGA分散体系中均存在层状液晶相, 层状液晶吸附在气泡的界面上. CGA稳定性可达20 h以上, 没有明显的相分离发生. 而分别由C12EO7和C12EO9制备的CGA呈现由胶束组成的连续相, 不存在液晶相结构, 因而其稳定性较差, 仅能维持数分钟. 实验结果表明, 层状液晶相结构可以显著提高CGA的稳定性. 其稳定作用的机理是通过影响泡沫排液过程, 增强Gibbs-Marangoni效应, 从而提高气泡液膜强度和减缓气相扩散速率.

Stability of Colloidal Gas Aphrons Prepared Solely by Nonionic Surfactant

Stable colloidal gas aphrons(CGA) were prepared solely by polyoxyethylene-type nonionic surfactant(C12EOn).Four different EO chain lengths namely C12EO3,C12EO5,C12EO7 and C12EO9 were considered.The microstructure and rheological properties on these colloidal systems were studied via optical microscopy and viscosimeter in attempt to explore the stability mechanisms.The experimental results suggest that CGA stabilized solely by C12EO3 and C12EO5 respectively exhibit the presence of lamellar liquid crystal adsorbed at the air/liquid interface,and could maintain more than 20 h without occurrence of collapse.In the case of CGA generated from C12EO7 and C12EO9,respectively,there is not any optical fine structure between two air bubbles and thus have a poor stability only for several minutes.It is concluded that the stability of CGA stabilized solely by C12EOn surfactants is attributed to the presence of lamellar liquid crystalline phases located at the gas/liquid interface.The role of liquid crystal in stabilizing CGA could be explained in several mechanisms including hydrodynamic drainage,the mechanical strength of the liquid film and the diffusion rate of entrapped gas.