A Conducting Nanocomposite of Polystyrene with Acetylene Black

Abstract

During recent years increasing research attention is being paid to the preparation of conducting nanocomposites of vinyl addition polymers like polystyrene (PS), 1 polypyrrole (PPY), 2 polyaniline (PANI), 3 polymethylmethacrylate (PMMA), 4 etc. with carbon nanotube (CNT). Most of these materials are being exploited in regard to their electrical properties including electrorheology. 5 In view of the difficulty of availability of carbon nanotubes and their high cost any cheaper alternative for the CNT component is these composites would be indeed worth exploring. In this context we have successfully used one cheap and abundant allotrope of carbon namely acetylene black (AB) as the nanocomponent. The particle size of AB is in the nano order range and the material is highly conducting. We have reported that N-vinyl carbazole (NVC) monomer can be readily polymerized in bulk or in toluene in presence of AB without any extraneous catalyst; and a PNVC-AB nanocomposite can be isolated from the system. The composite possesses high dc conductivity and enhanced thermal stability compared to PNVC homopolymer. 6 While extending the above procedures for polymerization vis-a-vis composite formation between AB and vinyl polymers such as PMMA, polyacrylonitrile (PAN) 7,8 it was noted that unlike NVC, acrylonitrile (AN) or methyl methacrylate (MMA) monomers could not be bulk polymerized by AB alone. We, therefore, modified the procedure in which MMA or AN monomers were dissolved in aqueous medium in which acetylene black was kept dispersed by sonication and nanocomposites of PMMA-AB and PAN-AB could be isolated. To prepare polystyrene–acetylene black nanocomposite (PS-AB) we used the emulsion polymerization process since styrene monomer is insoluble in water. Sodium dodecyl sulphate (NaDS) was used as an emulsifier and K2CrO4 and NaAsO2 were used as the redox initiator. Details of these procedures and bulk property characterizations of the PS-AB nanocomposite are highlighted in this article. It may be of interest to point out here that Choi et al. 1 reported the preparation of carbon nanotube (CNT) adsorbed polystyrene and PMMA microspheres by using nanotubes sonicated in aqueous solutions of the surfactants to which PS or PMMA microspheres were dropped. The conductivity values of 2 10 4 –3 10 5 S/cm were observed for CNT adsorbed on PS microspherers using cetavelon or sodium dodecyl sulphate as surfactant respectively.