Ionization Behavior and Spectral Properties of Polythiophene Hydrogels

The water-swollen poly(3-thiopheneacetic acid) (P3TAA) gels with various degree of cross- linkage (DCL) were synthesized. The swelling properties, dissociation behaviors, and spectral properties of P3TAA gels were studied. We have found that λ_max of UV-visible absorption spectrum of P3TAA gels increased largely around pH=5-6, which was similar to the linear polymer. However, a P3TAA gel showed no change in λ_max with the increase of temperature, unlike the linear P3TAA. These results suggested that conformational transition of the polythiophene main chain from nonplanar state to planar state was restricted due to the chemical cross-linkage of water-soluble polythiophene.