Soluble polyacetylene derivatives by chain-growth polymerization of dienes

A new method for the fabrication of soluble polyacetylene derivatives was developed based on bromination-dehydrobromination of bicyclic diene polymers. High molecular weight polymer precursors were synthesized by radical 1,4-polymerization of the corresponding dienes, which contained a bicyclo[2.2.2]octane skeleton. Polymer precursors with narrow molecular distributions were prepared by nitroxide-mediated polymerization of the bicyclic diene monomers. Regioselective elimination from the brominated polymer afforded a polyacetylene derivative contaning bicyclic substituents, which was readily soluble in common organic solvents. The polymer electronic bandgap, obtained by optical and electrochemical measurements, was in the range 1.4-1.7 eV. Low bandgap values were attributed to the conformational inflexibility of the bicyclic substituent forcing coplanar orientation of the backbone double bonds. Solid-state conductivity of the produced polymer in the undoped form was measured to be 1.5 × 10^-5 S/m. This new synthetic method allows for the chain-growth production of polyacetylene derivatives that possess favorable electronic properties and superior solubility characteristics to pristine polyacetylene.