Environmental responses of polythiophene hydrogels

A chemically cross-linked and water-swollen poly(3-thiopheneacetic acid) (P 3TAA) gel was synthesized, and its swelling and spectral changes associated with its ionization were studied. The gel undergoes an abrupt red shift in the electronic spectra at a certain pH, suggesting that a conformational t ransition due to ionization occurred despite the chemical cross-linkage. By changing the solvent composition, during cross-linking, gels with an enhan ced pi conjugated structure were prepared. By doping of P3TAA gel with a HC lO4 solution, a satisfactorily high electrical conductivity was obtained.