Investigating Dielectric and Mechanical Properties of Nano Composites of Polystyrene (PS), Polyaniline (PANI) &MoS2 Nano-sheets

Abstract

After the discovery of graphene and evaluation of its amazing properties, a whole new class of materials analogues to graphene was discovered. This class of 2D materials comprised of a wide range of materials, from pure elements to compounds i.e. Silicene, Germanene, Black Phosphorous & Transition metal di chalcogenides (TMDs) etc. These materials are categorized as 2D materials because they are just 1 atomic layer thick. MoS2, Molybdenum di Sulfide (Molybdenite), belongs to TMD’s class and is a semiconductor, having band gap of 1.8ev and Poisson’s ratio of 0.25. It has potential applications for flexible thin film transistors, optoelectronics, hydrogen storage, lithium ion batteries and other next generation electronic devices and Nano electro-mechanical systems. In this research, layered MoS2 is used as filler in the preparation of polymer Nano composites consisting of blend of PS and PANI while MoS2 nano sheets as filler. Polystyrene is an amorphous polymer, insulated in nature, having good mechanical properties while Polyaniline is a conductive polymer. Blending of such polymers could give new possibilities of wide range of dielectric, thermal and mechanical properties within a single system. In this study, first polymer blends of polystyrene and polyaniline were prepared by using solution blending method. Amount of Polyaniline was varied from 5wt% to 20wt%. Mechanical and dielectric properties were investigated using tensile testing machine and impedance analyzer respectively. It was found that tensile strength and young’s modulus of the PS/PANI blends were increased by 40% and about 79% respectively whereas elongation at break decreases to -64% for the blends as compared to the pure PS. Dielectric constant, dielectric loss and tangent loss at 100Hz increased up to the order of 103 , 105 and 102 respectively. AC conductivity increase in the order of 101 for (90/10) blend is observed at 100Hz. Based on these results, blend with ratio of 95% PS and 5% PANI was selected for final composite preparation. MoS2 nano-sheets were synthesized using Liquid Exfoliation method. These sheets were then dispersed at various concentrations, 0.3%, 0.5% and 1.0% (by weight) in the PS/PANI (95/5) polymer blends using solution casting method. It was found that tensile strength, modulus and strain ratio decreased by -50%, -42% and -79% respectively as compared to the PS/PANI blend having 5wt% of PANI (95/5) which was used as a matrix. Dielectric constant, dielectric loss, dissipation factor and ac conductivity increased for the hybrid composites as compared to the blend matrix.