Primary alkyl phosphine-borane polymers: Synthesis, low glass transition temperature, and a predictive capability thereof

With a multitude of potential applications, poly(phosphine-borane)s are an interesting class of polymer comprising main-group elements within the inorganic polymer backbone. A new family of primary alkyl phosphine-borane polymers was synthesised by a solvent-free rhodium catalysed dehydrocoupling reaction and characterised by conventional chemico-physical techniques. The thermal stability of the polymers is strongly affected by the size and shape of the alkyl side chain with longer substituents imparting greater stability. The polymers show substantial stability towards UV illumination and immersion in water however they undergo a loss of alkyl phosphine units during thermal degradation. The polymers exhibit glass transition temperatures (Tg) as low as -70 °C. A group interaction model (GIM) framework was developed to allow the semi-quantitative prediction of Tg values and the properties of the materials in this study were used to validate the model.