A recyclable PANI/PAAMPSA nanocomposite with repeatable, rapid, autonomous self-healing, and unprecedented electro-mechanical properties
Colton Duprey, Arya Ajeev, Dajung Hong, Katherine Webb, Sarah Veres, George Chen, Emily Linn, Gina Lusvardi, Zhongqi Liu, Ruigang Wang, Sanggyu Yim, Zhanhu Guo, Zachary J. Farrell, Luke A. Baldwin, Yang Lu, Ju‐Won Jeon, Evan K. Wujcik
Abstract
Polymer nanocomposites (PNCs) have been utilized in a number of applied areas including environmental engineering [ 1 , 2 ], aerospace [ 3 , 4 , 5 ], energy storage [ 6 , 7 , 8 ], and biomedical monitoring [ 9 , 10 ]. As bio-monitoring and wearable sensors have become a large area of interest, a definite need for wearable sensors that are flexible or stretchable, soft, and highly electrically conductive has emerged [ 11 , 12 , 13 , 14 ]. Typical inorganic electronic sensors are rigid and brittle, and the skin-inspired polymer electronics which allow wearers more flexibility and comfort, unfortunately, have issues with sensitivity as well as stability over time [ 9 , 10 ]. For a polymeric material to be used in a wearable sensor, it must possess comparable properties to the skin in terms of stretchability and elasticity. Self-healing is a highly beneficial attribute of biological systems. It allows them to autonomously repair materials in the event of mechanical damage, and this attribute is desirable in conductive polymers which will be used as wearable sensors. Polyaniline (PANI) is a well-studied conductive polymer which has acquired great interest due to its high conductivity as a result of its conjugated backbone; yielding itself to potential usage in electronics [ 15 , 16 , 17 ]. A conductive polyaniline (PANI)-based polymer complex with high stretchability and elasticity comparable to human skin, and autonomous, repeatable self-healing properties was developed previously [ 15 , 18 ]. The investigated polymer composite is composed of PANI, a small molecule dopant [phytic acid (PA)], and a polyelectrolyte [poly(2-acrylamido-2-methylpropane sulfonic acid) (PAAMPSA)]) [ 15 ]. PAAMPSA is a hygroscopic polymer electrolyte with a deprotonated sulfonic acid group. It is used to not only template the oxidative polymerization of aniline to form PANI but also to help utilize its electrolytic counterions to facilitate electron transport and increase conductivity. PA is a small molecule acid with six dihydrogen phosphate groups. The PA acts as both a P-type dopant to form the emeraldine salt form of PANI and a non-covalent crosslinker for the polymer matrix. The sulfonic acid and phosphate groups in the polymer complex allowed for copious hydrogen bonding and electrostatic interaction which yielded impressive mechanical properties, and the conductivity of the material measured to be 2 S/m [ 15 ].