Effect of Protonating Phosphoric Acid-Based Dopants on the Electroconductive and Mechanical Properties of Polyaniline/Poly(2-acrylamido-2-methylpropanesulfonic acid) Complexes
Arya Ajeev, Colton Duprey, Evan K. Wujcik
Abstract
This study aims to investigate the effects of using different small molecule dopants based on phosphoric acid such as nitrilotrimethylphosphonic acid (NTMPA), 1,1′-binaphthyl-2,2′-diyl hydrogenphosphate (BNHP), and pyrophosphoric acid (PPA) in a polyaniline/poly(2-acrylamido-2-methylpropanesulfonic acid) (PANI/PAAMPSA) polymer complex. The impacts of the size, structure, and number of acid groups of these small molecule dopants on the resulting solvent-cast film properties are examined. The polymer film is synthesized through a templated oxidative polymerization of aniline, where the resulting complex is noncovalently bonded via hydrogen bonding and electrostatic interactions. Fourier transform infrared spectroscopy confirmed the presence of a greater degree of hydrogen bonding in the PANI/PAAMPSA/PPA film, resulting in a greater elongation at break (ε = 3750%) and higher water content (16.3%). The stronger hydrogen bonding in PANI/PAAMPSA/PPA created robust cross-linking within the material, which reduced its ability to self-heal. On the other hand, the PANI/PAAMPSA/NTMPA film achieved high self-healing efficiencies of 98% (conductive self-healability) and 77.3% (mechanical self-healability) due to its more dynamic hydrogen bonding and electrostatic interactions. Furthermore, PANI/PAAMPSA/BNHP showed less hydrogen bonding, stretchability, and self-healing capabilities due to the steric hindrance and hydrophobicity caused by its rigid bulky structure compared to the more linear structures of the other dopants investigated.