Nanoscale cooperativity on a series of statistical methacrylates copolymers with electron donor–acceptor pendant groups

Abstract

Standard and StepScan DSC studies have been performed on a series of statistical methacrylate copolymers with electron-donor and electron-acceptor pendant groups that form intramolecular electron transfers. From standard DSC analysis we concluded that glass transition temperature slowly increased with increasing electron-acceptor monomeric moiety ratio up to 0.5 in the main chain. Using StepScan DSC method we calculated the size and volume of cooperative rearranging region as well mean temperature fluctuation at glass transition temperature. It was estimated also the average number of monomer units in the cooperative rearranging region. All parameters were calculated according to the method proposed by Donth based on Heat Capacity Spectroscopy. The results show that the presence of intermonomeric electron transfers decreased the chain mobility, as well as the cooperativity of relaxation processes of these structures in the glass transition range. This is reflected by minimal values of these parameters around 0.4 ratio of copolymer composition. Such behavior is similar to that of crosslinked or confined systems (e.g., nanocomposites, thin films) that have reduced chain mobility.