THERMOREVERSIBLE GELS OF POLYANILINE - VISCOELASTIC AND ELECTRICAL EVIDENCE ON FUSIBLE NETWORK STRUCTURES

We demonstrate thermoreversible gelation of a conductive polymer, i.e. , rubber-like melt processible electrically conducting compounds. Comb ination of viscoelastic and electrical conductivity measurements sugge sts network formation in the gel state and gel melting at elevated tem peratures. The gels have been prepared by dissolving polyaniline in do decylbenzenesulfonic acid (DBSA) using formic acid as a processing med ium which mas removed at the end. Importantly, without formic acid, re versible gelation and particle-free materials mere not achieved even a t the resolution of optical microscopy. For T < T-gel the materials be have elastically in compression experiments, the storage and loss modu li do not depend much on frequency, and the electrical conductivity is primarily electronic, probably due to high chain-to-chain hopping con ductivity. For T > T-gel the onset of liquid-like flow is detected usi ng modified ball drop method by dynamic mechanical analysis, the dynam ic moduli become strongly frequency dependent, and the electrical cond uctivity drops orders of magnitude to the value corresponding to the i onic conductivity of DBSA, suggesting that the chains are not in direc t contact. The physical crosslinks are probably localized mesomorphic domains which allow melting.