CONTROL OF IONIC-CONDUCTIVITY IN SOLID POLYMER ELECTROLYTE CONTAINING SPIROBENZOPYRAN DERIVATIVE BY PHOTOIRRADIATION

The solid polymer electrolyte composed of poly[(alpha-hydrooligo(oxyethylene)-omega-yl methacrylate] [P(MEO)OH], LiClO4 and a spirobenzopyran derivative (SP) has been prepared, and its photoinduced change in ionic conductivity has been also investigated. SP is a well-known photochromic material. SP is isomerized to photomerocyanine (PMC-form) upon UV irradiation. PMC-form is especially stable in protic solvents. This is attributable to the formation of hydrogen bond between PMC-form and the solvent. In the IR spectra of P(MEO)OH film, the absorption assignable to the 0-H stretching vibration shifts from 3501 cm-1 to 3480 cm-1 after UV irradiation for 2h. This also indicates the formation of a hydrogen bond between PMC-form and the hydroxyl group in the polymer side chain. The ionic conductivity of this film decreased upon UV irradiation and subsequently increased in the dark. This is attributed to the formation of hydrogen bond between PMC-form and P(MEO)OH by UV irradiation. Namely, this interaction acts as quasi-crosslinking point and this causes the ionic mobility change. Therefore, it was found that the ionic conductivity can be controlled by photoisomerization of SP in the solid polymer electrolyte upon irradiation.