Experimental and theoretical study of charge-transfer complex hybrid polyimide membranes

The nanostructure of sulfonated polyimide (SPI)/dihydroxynaphthalene (DHN) derivative charge-transfer (CT) complex hybrid films, which are noble alternative polymer electrolyte membranes (PEMs), is determined by a combined visible spectroscopy/quantum mechanical approach. From the visible spectra of SPI/2,6-dihydroxynaphthalene (2,6-DHN) and 1,5-dihydroxynaphthalene (1,5-DHN) CT complex hybrid films, it is confirmed that these films have different maximum wavelength, although difference of the molecular structure is small. From the calculation based on the experimental result, SPI and DHNs form multiple interactions consisting of not only CT interaction, but also hydrogen bonding in multilayered structures. CT interaction between SPI and DHN defines the DHN position in the SPI matrix, with DHN sitting in the cavity formed between SPIs. The molecular structure of the CT films derived from the multiple and complex interactions can recognize small differences in the structural isomers and bring changes of the optical property. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014, 52, 293-298 Many sulfonated polyimides (SPIs) have been actively investigated as polymer electrolyte membranes (PEMs) for polymer electrolyte fuel cells (PEFCs) as alternatives to Nafion. In this work, the molecular geometry of (SPI)/dihydroxynaphthalene (DHN) derivative charge-transfer complex hybrid films is determined by a combined visible spectroscopy/quantum mechanical approach. From the experimental and calculated results for SPI/2,6-DHN and 1,5-DHN, while the structural difference is small, different molecular geometries and optical properties can be seen.