Intrinsically Conducting Polymer Networks of Poly(thiophene) via Solid-State Oxidative Cross-Linking of a Poly(norbornylene) Containing Terthiophene Moieties

Herein we describe the preparation of intrinsically conducting poly(thiophene) via two different routes: solution- and solid-state cross-linking of terthiophene moieties. The solution-state cross-linking of terthiophene moieties was performed using conventional electrochemical polymerization in which insoluble cross-linked polymer was precipitated onto the electrode from electrolyte solution of the monomer by oxidative coupling of terthiophene units in the monomer, 5-norbornene- endo -2,3-bis(methylene-3‘-[2,2‘:5‘,2‘ ‘]-terthiophene acetate). In the alternative route, a precursor polymer, poly(norbornylene), prepared from the ring-opening metathesis polymerization (ROMP) of 5-norbornene- endo -2,3-bis(methylene-3‘-[2,2‘:5‘,2‘ ‘]-terthiophene acetate), was coated on either a conducting or insulating surface, and then the terthiophene units were cross-linked to form intrinsically conductive polymer (ICP) via electrochemical and chemical oxidation, respectively. More highly conjugated ICP was observed by performing oxidative cross-linking of the polymer in the solid state, in contrast to the cross-linked intrinsically conducting polymer prepared via electrochemical polymerization of 5-norbornene- endo -2,3-bis(methylene-3‘-[2,2‘:5‘,2‘ ‘]-terthiophene acetate) from solution. Electrical conductivities for the polymers obtained via solid-state chemical oxidative cross-linking were on the order of 1 × 10 -3 S/cm.