A new microwave ‘smart window’ based on a poly(3,4-ethylenedioxythiophene) composite

Abstract

The preparation and dc and microwave characterisation of a new microparticulate mixed polymeric conductor containing poly(3,4-ethylenedioxythiophene) (PEDOT) and copper metal in a poly(ethylene oxide)–Cu(BF₄)₂–LiBF₄ polymer electrolyte matrix is described. The composites exhibit large, rapid and reversible changes in their microwave transmission coefficients when small dc or ac fields (5–7 V) are applied radially across annular samples (13 mm o.d.) from the edges. At 1 GHz, changes of −6 dB (0 V) to −15 dB (5 V) with switching speeds of ≤250 ms were observed, and −2 to −12 dB at slower rates. Single cell experiments show that redox processes are confined to thin surface layers of the PEDOT particles. A mechanism for switching involving the polarisation of PEDOT particles under an applied field is proposed.