Highly Stretchable, Conductive, and Transparent PDMS Island-Continuous PEDOT:PSS Matrix Composite Electrodes

A polymer component in immiscible polymer blends results in phase separation, leading to polymer morphologies that vary from isolated spherical particles to a continuous matrix phase depending on the polymer weight ratio. This work demonstrates that a polymer component with a low weight fraction can form a continuous matrix phase, rather than isolated spherical particles, which is unprecedented. Bar-coating a solution of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) blended with a high fraction of polydimethylsiloxane (PDMS) and a surfactant results in a continuous PEDOT:PSS matrix distributed with spherical PDMS islands. The PEDOT:PSS and PDMS in the coated layer phase separate, forming a bilayer structure owing to its different affinities to the poly(ethylene terephthalate) (PET) substrate. When cured at 100 & DEG;C, water and other volatiles in the PEDOT:PSS phase in the bottom layer evaporate, generating spaces that are subsequently filled with PDMS from the phase-separated top layer. The continuous PEDOT:PSS matrix ensures excellent conductivity (66.17 & omega;& BULL;sq(-1)), while the PDMS islands provide high stretchability. The electrical conductivity of the new electrodes varies negligibly when stretched at 50% strain and is even maintained up to 150% strain. The electrodes exhibit high transparency (& AP;90% at 550 nm) and electromechanical stability over 1000 cycles of 30% stretch/release tests.