Polypyrrole thermally sensitive polyelectrolyte composite (I)

Polypyrrole (PPy) was prepared by electrochemical polymerization with the p olyelectrolyte (PE) as a dopant. The PEs were copolymers of the water solub le polymers and 2-acrylamido-2-methyl-1-propane sulfonic acid (AMPS). The w ater soluble polymers were thermally sensitive poly(N-isopropyl acrylamide) , P(NiPAAm) and thermally insensitive poly(acrylamide), P(AAm). The surface of PPy/PE film observed by SEM was smoother than that of PPy film doped wi th a monoelectrolyte. PPy/PE composites were fairly conductive, whose elect rical conductivities measured by the four-probe method were in the range of 10(-1) to 10(-2) S/cm. The characteristics of cation and anion exchange du ring redox processes were investigated by applying potential from -0.8 to 0 .5 V vs, an Ag/AgCl reference electrode to the PPy. The effect of temperatu re on the doping-dedoping behavior and mass change of PPy composites was in vestigated by potentiodynamic voltammetry and electrochemical quartz crysta l microbalance (EQCM). The electrochemical activity of the PPy/PE gradually decreased with increasing temperature. PPy/P(NiPAAm/AMPS) showed much grea ter mass change with increasing temperature than PPy/P(AAm/AMPS), mainly be cause of a decrease in the degree of swelling of thermally sensitive moiety . This confirms that PPy/P(NiPAAm/AMPS) possesses temperature-dependent ele ctrochemical activity, which indicates that it can be utilized for many att ractive applications. The thermal volume transition temperature of PPy/P(Ni PAAm/AMPS) was estimated from the slope change of mass decrease. The transi tion temperature of the oxidized state of PPy/P(NiPAAm/AMPS) was higher tha n that of the reduced state. (C) 1999 Elsevier Science S.A. All rights rese rved.