Thermoreversible polyaniline gels

Abstract

Polyaniline (PANI) forms thermoreversible gels in different sulphonic acids e.g. dinonyl napthalene sulphonic acid (DNNSA), dinonylnapthalene disulphonic acid (DNNDSA), ± camphor - 10 - sulphonic acid (CSA) and dodecyl sulphonic acid (DSA) when processed from the formic acid medium. The surfactant concentration has been varied from weight fraction of PANI (W_PANI)=0.05-0.60. In most cases at W_PANI=0.05-0.40 compositions fibrillar network structures are observed from SEM study. They also exhibit reversible first order phase transition during both heating and cooling in DSC. The melting temperature and the gelation temperature increases with increase in surfactant concentration of the gel. From the WAXS pattern it is concluded that crystallization of the surfactant tails anchored from the nitrogen atom of PANI through its SO₃ H head group is responsible for gelation. The conductivity of all the gels with increase in PANI concentration showed a maximum with composition. The maximum conductivity is ~0.01 S/cm, for W_PANI=0.22. The conductivity variation has been explained by considering it as a function of both interchain and intrachain contributions.