New Strategy for Synthesizing Catalyst-free HCl-doped Polyaniline

A new low-cost strategy for the catalyst-free synthesis of HCl-doped polyaniline (PANI) was developed. A 50:50 (water/hydrogen peroxide) solution was used as an oxidant and a 1M HCl solution was used as an acidic dopant. The synthesis was simple and was carried out at $4 ^{\circ}\mathrm{C}$ without mechanical or magnetic agitation. The volume ratio for aniline to hydrogen peroxide was 3:1. It is proposed that the reaction proceed through radical polymerization, in which hydroxyl radicals (OH•) are generated by the action of hydrogen peroxide (H2 O2) to polymerize aniline. The formation of HCl-doped Polyaniline (PANI) was confirmed using of Fourier-transform infrared spectroscopy, UV-Vis spectroscopy, and thermogravimetric analysis. The purification process is easier, and the risk of harmful byproducts is reduced as the reaction continues under benign conditions. Additional benefits of using H2 O2 as an oxidizing agent include higher polymer purity, increased scalability, and improved control over polymerization kinetics. Overall, this novel synthetic approach using 50:50 (water/hydrogen peroxide) as an oxidizing agent for PANI offers a promising avenue for efficient, sustainable, facile, and catalyst-free production of HCl-doped PANI, with potential uses in a plethora of areas, including electronics, energy, and sensing of volatile gases at relatively low concentrations. The synthesized polyaniline film exhibited good conductivity $\left(0.010197 \pm 0.000174 \mathrm{Sm}^{-1}\right)$ and low resistivity $(100.6535 \pm 1.64424$ $\left.\Omega \mathrm{m}^{-1}\right)$. The addition of Cetyl Trimethyl Ammonium Bromide (CTAB) as a modification agent imparted hydrophobic properties to the initially hydrophilic polyaniline. This modification resulted in a significant increase of approximately 290% in the contact angle, indicating enhanced hydrophobicity.