Membrane Structure and Permeation Property of Polymer/Liquid Crystal Composite

Tisato Kajiyama Faculty of Engineering, Kyushu University, Fligashi-ku, Fukuoka 812 A bimolecular membrane of phospholipids such as lecithin is in a state of liquid crystal capable of reversible structural modifications and its permeation property depends on such reversible change. Artificial amphiphiles with monoalkyl and dialkyl groups form multilamellar liposome composed of the bimolecular layer. Artificial amphiphiles have characteristics of both thermotropic and lyotropic mesomorphisms. The diffusive permeability of polymer/artificial amphiphiles composite membrane to water exhibits a distinct jump in the vicinity of the crystal-liquid crystal phase transition temperature. Diffusive permeability coefficients (P) to hydrocarbon gases for polymer/liquid crystal (EBBA) composite membrane reveals a distinct increase of 100-200 times over several degrees in the crystal-liquid crystal phase transition temperature range of EBBA. P decreases with increasing the number of carbon atome below the phase transition temperature and this trend suggests that permeation is predominantly governed by diffusion process. On the other hand, above the phase trasition temperature of EBBA, P increases with an increase of the number of carbon atom. This tendency can not be explained by diffusion control mechanism but it is reasonably expected that permeation is mainly governed by solubility process.