Colloidal dispersions of conducting copolymers of aniline and p-phenylenediamine for films with enhanced conductometric sensitivity to temperature

Polyaniline colloids stabilized with poly(N-vinylpyrrolidone) were prepared by the oxidation of aniline with peroxydisulfate. The replacement of a part of aniline with p-phenylenediamine converted the original globular colloidal particles into nanofibers, which is a favorable morphology for the deposition of conducting patterns, but the colloidal stability was retained. The corresponding poly(aniline-co-pphenylenediamine) powders have been characterized using FTIR spectroscopy. The copolymers have a more pronounced temperature dependence compared with the parent polyaniline; the ratio of the conductivity at 300 and 100 K is 24 for polyaniline, 235 for a copolymer containing 20 mol% p-phenylenediamine, and 3690 for 30 mol% p-phenylenediamine. Due to their fibrillar morphology, copolymer colloids prepared with 10 and 20 mol% p-PDA produced films with conductivity nearly three orders of magnitude higher than that from globular PANI colloids. The conductivity of the film cast from the copolymer colloid prepared with 20 mol% p-PDA exhibits a temperature dependence much steeper than its powder counterpart. The processable copolymer colloids are thus well suited for the preparation of conducting temperature-sensitive films.