Highly porous polyaniline (PANI): a novel green catalytic method for morphology control

Abstract

Conducting polymers (CPs) combine the electric charge conduction properties of metals with polymers’ advantages. Among CPs, polyaniline (PANI) is unique for its characteristics and physico-chemical properties. PANI traditional synthesis, based on the oxidative polymerization of aniline by strong inorganic oxidant, is still the most employed, albeit it leads to a large amount of toxic and carcinogenic waste. This approach has become less practicable in the last years due to stricter rules on environmental protection and pollution limits. Therefore, the possibility of using more environmentally friendly oxidants and alternative reaction mechanisms, which avoid the production of toxic by-products, represents an attractive goal. Based on these aspects, a new synthetic method has been developed in the last years, starting from more sustainable reagents (N-phenyl-p-phenylenediamine and molecular oxygen or hydrogen peroxide), demonstrating improved biocompatibility of the obtained polymer. However, PANI from aniline (PANI1) and that from N-phenyl-p-phenylenediamine (PANI2) differ, particularly in terms of morphology, porosity (porous PANI1 and compact PANI2), and conductivity (higher for PANI1). Since it is not clear which parameters are mainly affecting the final properties of PANI2, the goal of the present work is investigating the mechanisms involved in the synthesis of the two materials to modulate and enhance the final properties of PANI2, making it a sustainable alternative to traditional PANI1. Finally, for the first time, a comparative life cycle assessment (LCA) study was conducted on PANI synthesis to compare the traditional method (PANI1) and the “green” one (PANI2) to determine whether the latter truly reduces the environmental impact.

Graphical abstract