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

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 2 6 dB (0 V) to 15 dB (5 V) with switching speeds of less than or equal to250 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.