Synthesis and Study of Electrical and Mechanical Properties of Polypyrrole/SIS Copolymer Blends and Bimetallic Polymeric Nanocomposites

Abstract

Conductive polymers such as polypyrrole, polythiophene and polyaniline have received significant attention because of their outstanding and attractive electronic, optical, conductive and redox properties. Among all conducting polymers, polypyrrole has gained greater interest due to its high conductivity along with good thermal and environmental stability. Polypyrrole can be easily oxidized both chemically and electrochemically. It (PPy) is widely used in batteries, sensors, super-capacitors, microwave shielding, corrosion protection, electrical wiring coating, and radar absorption. Due to the strong inter and intramolecular interactions and cross linking of PPy chains, it is not soluble in organic solvents and water. Because of its rigid ring structure, polypyrrole is very brittle, inflexible, exhibits poor processability and lacks mechanical or film forming properties. Stability of polypyrrole films can be achieved by forming blends of polypyrrole with different insulator, thermoplastic copolymers. In this research work blends of polypyrrole have been formed with poly(styrene-isoprene-styrene) (SIS) thermoplastic insulating copolymer by loading polypyrrole within the range of 6-15 wt.%. In SIS copolymer polystyrene has glassy domains dispersed in the flexible polyisoprene matrix, giving an overall flexibility to polypyrrole in blend, enhancing mechanical strength of PPy with the enhancement of electrical conductivity of insulator SIS copolymer. FTIR analysis has confirmed the incorporation of polypyrrole in to SIS copolymer. Electrical conductivity of blends was measured by two-point method and mechanical properties were determined through mechanical testing of each blend. Enhancement in electrical conductivity and mechanical properties was reported with the increase in PPy loading into SIS copolymer and the best results were obtained with 15 wt% PPy/SIS blend. Conductivity and mechanical strength of 15 wt. % PPy/SIS blend was tremendously increased further by the addition of Ag-Pd bimetallic nanoparticles as nanofiller. A novel ecofriendly, green technique was used for the synthesis of Ag-Pd bimetallic nanoparticles. In this work, Camellia sinensis (green tea) extract was used for the first time to synthesized bimetallic Ag-Pd. XRD analysis has confirmed the pure Ag-Pd bimetallic nanoparticles were synthesized with an average crystallite size of 7.9 nm. 14 FTIR analysis indicates the presence of different capping agents over the surface of synthesized nanoparticles. Elemental composition of synthesized nanoparticles was determined by EDX analysis. In order to enhance mechanical and electrical properties of 15 wt. % PPy/SIS blend, Ag-Pd bimetallic nanoparticles were loaded within the range of 1-5 wt. % to form nanocomposites. Enhancement in the electrical and mechanical properties was observed with the increasing amount of Ag-Pd nanoparticles.