Photo-controlled K⁺ Permeation of Polymer/Liquid Crystal Composite Thin Film Containing Photoresponsive Crown Ether

A ternary polymer/liquid crystal/photorespbnsive crown ether composite membrane of several tens of nm in thickness was prepared by a water-cast method. A ternary composite thin film was prepared by building up several tens of layers of the water-cast composite membrane. Two types of photoresponsive crown ethers, AZO-CR (1) and AZO-CR(2) as shown in Fig. 1 were used. The aggregation state of the composite membrane was investigated by transmission electron microscopic observation and DSC measurements. These measurements revealed that the liquid crystalline material formed a continuous phase interpenetrating with the spongy three-dimensional network of PVC. It was also confirmed that photoresponsive crown ether molecules were dispersed almost molecularly in liquid crystal domains. These results indicate that liquid crystal domains can play a role as a transporting phase for carriers and penetrants. The UV absorption measurements upon UV and VIS irradiations reveal that trans-cis photoisomerization of photoresponsive crown ether ocurred even in the ternary composite thin film. The photoresponsive facilitated transport of K⁺ through the polymer/liquid crystal/AZO-CR(1) composite thin film was investigated. Also, the active transport of K⁺ driven by photoirradiation and pH gradient through the ternary composite thin film containing AZO-CR(2) was investigated.