Ionic and Nonionic Waterborne Polyurethane and Blend Nanocomposites of Polyaniline and <scp>MWCNT</scp> for Piezoresistive Application

ABSTRACT With the continuous advancement of smart wearables and flexible electronics sensitive to strain, eco‐friendly candidates have gained growing interest. Polyurethanes (PUs), with their flexible and tough nature, are prime candidates as the matrix for these strain sensors. Waterborne PUs (WPUs), as an environmentally‐friendly group of PUs, are also gaining interest in this field. In this regard, we synthesized WPUs using ionic and nonionic internal emulsifiers, and their capability to suppress colloidal aggregation was evaluated by the dynamic light scattering method and the Sparse Bayesian Learning calculation. The results showed higher efficiency of the ionic emulsifier. Polyaniline (PANI), as a biocompatible polymer, was added to the selected WU to improve its modulus, thermomechanical performance, and electrical conductivity. PANI particles enabled reaching electrical percolation of multi‐walled carbon nanotubes (CNTs) at low content (0.5 wt.%). The relative electrical resistance was used as a representation of piezoresistivity, and the blend nanocomposites of the selected WPU, PANI, and CNT showed strain sensitivity over a wide range of strain (70%). The PANI particles could have assisted electron tunneling when the CNTs separated by considerable distances. These blend nanocomposites could be considered a promising candidate for flexible strain sensors in applications with large deformations, like body movement.