Multifunctional electromechanical and thermoelectric polyaniline-poly(vinyl acetate) latex composites for wearable devices

Abstract

This paper reports on the piezoresistive, thermoresistive and thermoelectric behaviour of polyaniline-poly(vinylacetate) (PANI-PVAc) nanocomposites prepared by simple, scalable, green latex technology. The relationship between the electrical properties and the PANI-PVAc ratio was analyzed in the framework of the percolation model and related to morphological and structural changes. Composites with 10, 20 and 30 wt.% PANI combine suitable electrical conductivities and the beneficial mechanical properties of the polymer matrix with hardly decreasing the polymer matrix thermostability. They exhibit satisfactory electromechanical and thermoresistive properties to be used for sensor applications. Both the Gauge factor (GF) and thermal sensitivity decay for PANI contents beyond the percolation threshold. Composites with 10 wt.% PANI achieve the highest GF up to 12 for 10% deformation and a thermal sensitivity of 0.25 %•C-1 between 20-40 ºC, suitable for flexible and wearable temperature sensors for monitoring human health. Composites with 20 wt.% PANI are appropriate for larger strain deformations and have superior fatigue resistance. The high electrical conductivities of samples with 20 and 30 wt.% PANI are essentially preserved after large deformations of  300%, which is important in the design of stretchable elastomer conductors; they both provide the best compromise between thermoelectric (ZT) and mechanical properties. This tunability together with the soft nature of composites paves the way for low-cost, macroscale, diverse applications such as strain and temperature sensors in stretchable and wearable electronics.