Langmuir-Blodgett films of conducting diblock copolymers

Novel amphiphilic block copolymers have been synthesized via ring-opening metathesis polymerization (ROMP), where one block is a precursor to a water-soluble polymer and the other block is a precursor to polyacetylene. The water-soluble block is made from a silyl ester protected carboxylic acid functionalized polymer. The silyl ester groups are used to protect the ROMP initiator from the carboxylic acid groups during polymerization and are easily deprotected afterward. The polyacetylene precursor block is made via ROMP using an approach known as the "Durham" route to polyacetylene. These amphiphilic block copolymers are surface active and quite amenable to the Langmuir-Blodgett (LB) technique, whereby films of these materials were fabricated and converted to polyacetylene-containing films by heating. UV-visible spectroscopy showed that the polyacetylene chains are oriented mostly in the plane of the LB film and in the dipping direction of the substrate. Upon doping with iodine, these films were shown to have better conductivities than either spin-coated or bulk cast films made from the same materials. The higher conductivity is explained by the high degree of order imparted using the LB technique.