Investigations were carried out on the effect of photoirradiation on the alkali metal ion permeability of poly (vinyl chloride) (PVC) membranes entrapping photoresponsive crown ethers (3, 4-(l, 4, 7,10,13-pentaoxatridecane-l, 13-diyl)benzyl(phenylazo)benzoate [ 1 ] and 4, 4'-bis [3,4-(l,4,7,10,13-pentaoxatridecane-l,13-diyl)benzyloxycarbonyl]azobenzene [i]). The photo-responsive crown ethers [I] and  were isomerized from trans-form to cis-form and vice versa in the PVC membranes by ultraviolet (UV) and visible (VIS) light irradiation, respectively (Figures 2 and 3). The WC\trans- membrane was found to permeate alkali metal picrates with the selectivity in order of K+ > Rb+ > Na+ > Cs+ (Tables 4 and 5). The permeation rate of K+ was accelerated by UV irradiation, while the acceleration for the other cations was not pronounced. The acceleration of K+ permeation rate was explicated in terms of enhancement of the K+ concentration in the membrane. On the other hand, in the case of the PVC/C membrane, photoirradiation had little influence on the permeability for alkali metal-ions (Table 3). In order to estimate the cation-binding abilities of [ 1 ] and  the liquid-liquid extractions were carried out before and after irradiation (Tables 1 and 2). The K+ selectivities in extraction (K+/NaS) of 1.7 and 2.2 were observed for trans- and UV-irradiated , respectively. The cation binding ability of  was not affected by UV irradiation. These results suggest that cis- effectively binds K+ ion as an intramolecular sandwich-type complex.
ASJC Scopus subject areas
- Chemical Engineering(all)