New conductive thermoplastic elastomers. Part II. Physical and chemical-physical characterization

To overcome the problems relevant to the low processbility and scarce mechanical properties of polyaniline, in a previous work we have proposed the synthesis of elastomeric conducting copolymers prepared by grafting polyaniline (EB) or sulfonated polyaniline (SPAN) chains to the backbone of a carboxylated segmented polyurethane (PEUA). In the present work the physical and chemicalphysical properties of the copolymers are investigated. As evidenced by thermal (DSC) and dynamo-mechanical (DMTA) characterization, the introduction of EB or SPAN in the matrix enhances the hard-soft phase segregation effect, because of the strong tendency of the conductive polymer chains to aggregate. Moreover, the EB and SPAN chains, grafted to the polyurethane backbone, acting as reinforcing filler, give rise, compared with the mechanical properties of the insulating matrix, to an increase of the Young modulus and a decrease of the tensile set. When the copolymers are HCl doped their electrical conductivity increases many orders of magnitude, reaching values of about 10(-3) Omega(-1) cm(-1). The conductivity, measured along the deformation direction, may be further increased by stretching the copolymer films. (C) 2002 Wiley Periodicals, Inc.