Tuning the Structural, Mechanical, Thermal and Electrical Properties of in-Situ Polymerized Polyindole/Carboxymethyl Chitosan/Nickel Oxide Blend Nanocomposites for Energy Storage Applications

The main objective of the present study was to develop flexible conductive biopolymer blend nanocomposites using polyindole (PIN) and carboxymethyl chitosan (CMC) with various nickel oxide (NiO) nanoparticles by in-situ polymerization techniques. Different techniques were used to study the effect of NiO content on the structural, optical, morphological, thermal, mechanical and electrical characteristics of PIN/CMC blend nanocomposites. Fourier-transform infrared spectroscopy (FT-IR) demonstrated that the introduction of NiO nanoparticles resulted in chemical bonding with the PIN/CMC blend, as evidenced by the formation of a new peak at a wavenumber of 603 cm^− 1. The lowest optical bandgap energy was found in 10 wt% composites. The increased crystallinity of the blend nanocomposites was evident from X-ray diffraction (XRD) patterns. The scanning electron microscopy (SEM) and the energy dispersive X-ray (EDX) analysis confirmed the presence of NiO nanoparticles in the PIN/CMC blend. High-resolution transmission electron microscopy (HR-TEM) images revealed that the NiO particles were homogeneously dispersed in the blend matrix at a manometer scale. The thermogravimetric analysis (TGA) demonstrated that the reinforcement of NiO significantly improved the thermal stability of PIN/CMC blend from 202 to 223 °C. Electrical conductivity improved significantly as the temperature and nanoparticle dose increased. The tensile strength of the 7 wt% NiO-loaded PIN/CMC blend nanocomposite was 102% higher than that of the pure PIN/CMC blend. This PIN/CMC/NiO nanocomposite has high tensile strength, thermal stability, dielectric constant and electrical properties, making it suitable for a wide range of applications, including energy storage and flexible nano-electronic devices.