Electro-Magneto-Optically Active Polyaniline/Hydroxypropyl Cellulose Composite

A polyaniline (PANI) composite was prepared through chemical polymerization of aniline in the cholesteric liquid crystal (CLC) state of hydroxypropyl cellulose (HPC). Polymerization and composite formation were simultaneously performed. Polarizing optical microscopy, scanning electron microscopy, electrochemistry, and optical spectroscopy were used to characterize the composite. Electron spin resonance and a superconducting quantum-interference device were used to investigate the composite’s magnetic properties. PANI in the composite exhibited a helical structure of the main chain as a result of the main chain growing in the direction of the LC orientation. The main chains of PANI were secondarily doped, thus they exhibited moderate electrical conductivity as a conducting polymer (PANI)/insulating polymer composite. Polarons (radical cations) distributed along the main chain with a helical structure are responsible for the composite’s magnetic spins. Consequently, the spins, like the helical structure, are delocalized. Because of the doping–dedoping of the PANI component, the composite exhibits excellent redox properties. The PANI/HPC composite’s potential applications in capacitors, electrochemical transistors, thermistors, and optical fibers were investigated.