Charge transport and conductivity measurement in polyaniline-poly(vinyl acetate) blends

Abstract

Poly(vinyl acetate) (PVAc) is used extensively in coatings, adhesives and films. The carbonyl group (C=O) in the structure of PVAc forms hydrogen bonding with amine and hydroxyl groups and this may also enhance miscibility with polyaniline. Hence, PVAc has been chosen for blending with PANI. Further, PVAc can be used in moisture sensors and after blending with PANI its conductivity would be in semi conducting range with moisture response, which will be suitable for easy measurement. It was expected that, the given blend may give higher conductivity because 1) PVAc and PANI solubility parameter values match closely: the Hilde Brand solubility parameter (δ) of aniline is 21.1 Mpa 1/2 and PVAc is found to be 20 Mpa1/2, 2) Its miscibility also increases due to H-bonding forces of attraction observed in amine group of PANI and 'CO' group of PVAc. 3) PVAc has excellent sticking properties to different substrates which makes it useful as an adhesive and 4) Work function values of PANI as well as PVAc match closely. It is interesting to mention that PVAc has a low Tg (28 °C) and thus may serve as a polymeric plasticizer for PANI, which would help to improve processability and/or film formation. There are many methods of blending polymers but only limited techniques can be applicable for conducting polymers. PVAc is soluble in high dielectric constant solvent such as methanol. However, PANI is not soluble in this solvent even after modification with suitable dopants. Hence, a new method has been adopted for blending these two components; i.e. the in situ blending method. This system also explains ex-situ blending method, electrical properties and charge transport processes in the blend.