Evaluation of Small Molecule Dopants in Self-Healing Conductive Polymer Complex PANI:Paampsa.

Self-healing is a highly beneficial, and desirable, attribute of biological systems that allow them to autonomously repair surfaces in the event of mechanical damage. Recently, flexible/stretchable electronics and wearable sensor researchers have been motivated to imitate this behavior in innovative devices with unique and unprecedented electro-mechanical properties. Conductive self-healing polymers have been utilized to improve a range of electronic and optoelectronics devices, including wearable sensors and displays for healthcare,[1] virtual reality, and soft robots, among many others.[2] For a polymer to be used in wearable sensors, it must possess comparable properties of skin in terms of stretchability (maximum strain), elasticity (Young’s modulus), and self-healing—being able to regain both mechanical and electronic properties with a high efficiency. Self-healing properties are necessary to be resistant to internal and/or external mechanical damages caused by wear and tear, cuts, and rips.[8] Additionally, the polymer sensors must have excellent mechanical properties with a high conductivity for sensitive measurements that are reliable and repeatable.

To this effect, our laboratory has previously developed a conductive polyaniline (PANI)-based polymer complex with high stretchability, elasticity comparable to human skin, and autonomous, repeatable self-healing properties.[3] However, further improvement of conductive and electronic sensitivity is desirable to accurately measure slight changes in movement or pressure. To accomplish this, alternative small molecule dopants (SMD) have been added in replacement of the previous dopant, phytic acid. The investigated polymer composite is composed of PANI, a small molecule dopant, and a polyelectrolyte [poly(2-acrylamido-2-methylpropane sulfonic acid) (PAAMPSA)]. The SMDs being evaluated for this polymer are 1) trimethyl 1,3,5-benzenetricarboxylate, 2) 1,2,4-benzenetricarboxylic acid, 3) trimesic acid, 4) formylbenzene which will be referred to as SMD1, SMD2, SMD3, and SMD4, respectively, for this experiment.

The implications from this study will seek out to ameliorate the performance, accuracy, and robustness of polymer sensors in wearable applications. The ability to monitor subtle changes in physiological signals using flexible electrical devices can be valuable for detecting disease through continuous comfortable monitoring as well as be applied for human pulse detection, speech recognition, and electrical artificial skin. The ideal polymer would have high conductivity, elasticity, self-healing capabilities, tensile strength, omnidirectional stretching, and would be scalable at a low cost.

[1] E. K. Wujcik, et al. IEEE Sens. J. 2013, 13, 3430;

[2] C. X. Zhan, et al. Journal of Materials Chemistry C 2017, 5, 1569;

[3] Y. Lu, Z. Liu, H, et al, ACS Appl Mater Interfaces 2019, 11, 20453.