Role of Small Molecule Dopants on the Synthesis, Structure, Electro-Mechanical, Self-Healing Properties and Working Relationships of PANI/PAAMPSA Systems

Stretchable electronic polymer (SEP) sensors have attracted significant interest due to their distinctive properties and versatile applications in the field of healthcare, artificial skin, human-machine intelligence etc. The development of lightweight, self-healable, stretchable, and high functioning components stands as a major requirement in wearable electronics, in consideration of the rigid metal and metal oxide-based sensors. In this work, the SEP system is composed of polyaniline (PANI), poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (PAAMPSA) and small molecule dopants (SMDs). The polymer system is synthesized through the oxidative polymerization of aniline while, A-PAM acts as a template to guide the PANI polymerization. SMD and A-PAM acts as dopants and cross-linking agents. This study explores the effects of SMDs with functional groups—carboxylic (-COOH), sulfonic (-SO3H), and phosphonic (-PO3H)—on the PANI/PAAMPSA system, investigating their influence on the material's thermal behavior, morphology, self-healing abilities, and electro-mechanical properties. Sulfonic acid groups were found to enhance electrical conductivity due to their stronger acidity and ionic interactions. Among the SMDs investigated, 4-dodecyl benzene sulfonic acid exhibited a conductivity of 0.07 S/m and a Young’s modulus of 39.76 kPa, while SMDs like pyrophosphoric acid, trifluoromethane sulfonic acid, and 5-sulfosalicylic acid dihydrate demonstrated exceptional stretchability, reaching up to 4000%.