Flexible, Highly Transparent, and Conductive Poly(3,4-ethylenedioxythiophene)-Polypropylene Composite Films of Nanofibrillar Morphology

A novel chemical strategy for fabricating flexible, transparent, and conductive poly(3,4-ethylenedioxythiophene) (PEDOT) films with a nanofibrillar morphology by in situ deposition on commercial plastic substrates has been developed. The key points of the strategy include (1) preimplanting surface sulfate groups (SO4-) onto the substrate surface by a confined photocatalytic oxidation (CPO) technique, which was critical both for improving the adhesion of the PEDOT with the substrate via static interactions and for inducing polymerization of EDOT onto the substrate surface, and (2) deliberately controlling the nanofibrillar network morphology by means of the reaction recipe and parameters, which was critical for balancing conductivity and transparency. On the basis of this design, with BOPP as a model substrate, PEDOT-BOPP composite films approximately 20 nm in thickness with a transparency as high as 90% and a conductivity of 300 S/cm were obtained. Moreover, XPS data demonstrated that the SO4- implanted on the substrate surface constituted the primary dopant of the deposited PEDOT, and peeling tests with 3M Scotch adhesive tape proved that the adhesion between the substrate and PEDOT was drastically enhanced. Combined with a photomask, a PEDOT micropattern on the polymer substrate could also be fabricated.