Novel Conjugated Polymer Containing Aromatic Ring and Selenium in Backbone. Side Reactions in the Addition Polymerization of Benzenediselenol to Diethynylbenzene

Abstract

Irregular linkage in polymers obtained by the radical addition polymerization (so called polyaddition) of 1,4-benzenediselenol (BDSe) to 1,4-diethynylbenzene (DEB) was investigated. BDSe and DEB were polymerized by UV-irradiation in toluene at 60°C under nitrogen atmosphere to give a pale-yellowish polymer in 71% for 6 min. A diselenide linkage was found in the obtained polymer by Raman spectroscopy. A coupling reaction between seleno radicals may occur in the course of the polymerization. The extent of diselenide linkage (–Se–Se–) was estimated to be one unit against 82±5 repeating units (–CH = CH–⌬–CH = CH–Se–⌬–Se–) from the Raman intensities of the diselenide linkage at 271 cm−1 relative to 1,4-diselenophenylene group (–Se–⌬–Se–) at 1055 cm−1. The effects of the polymerization conditions were also investigated. The coupling reaction between seleno radicals occurred more frequently when excess BDSe was used in the monomer feed ratio. The polymerization temperature and concentration of added oxygen in the reaction vessel affected little the diselenide linkage. The electrical conductivity of the polymers was of the order of 10−10 S cm−1 without dopant and 10−7 S cm−1 on I2 doping regardless of the content of the diselenide linkage in the polymers. The diselenide linkage in the polymers did not reflect appreciably the electrical conductivity of the polymer.