Synthesis of conjugated polymers by vapor deposition polymerization

Abstract

The synthesis of poly(2,5-thienylene vinylene) and poly(4,7-thianaphthene) by vapor deposition polymerization is presented. 2,5-Di(bromomethyl)thiophene was subjected to vapor phase pyrolysis at 550 degrees C to form a reactive intermediate. Upon condensation, the reactive intermediate polymerized spontaneously at a temperature higher than -25 degrees C to produce poly(2,5-thienylene vinylene). The obtained poly(2,5-thienylene vinylene)s were fractionated into THF soluble and insoluble fractions. The number average molecular weights of the THF soluble fractions range from 1500 to 4000 as determined by GPC measurements. The obtained polymer shows no glass transition and melting point on the DSC scans. Doping of a poly(2,5-thienylene vinylene) film with I-2 vapor led to a conductivity of 1 x 10(-4) S cm(-1). In the second part of this study, 2,3-diethynylthiophene was subjected to vapor phase pyrolysis at 300 degrees C to yield a reactive intermediate, 4,7-dehydrothianaphthene. Upon condensation, the obtained 4,7-dehydrothianaphthenene was polymerized spontaneously at a temperature higher than -25 degrees C to produce poly(4,7-thianaphthene). The obtained poly(4,7-thianaphthene) was insoluble in common laboratory solvents and shows also no melting point and glass transition on the DSC scans.