Investigation of the microrheological properties of the branched polystyrene using 2-(2-bromoisobutyryloxy) ethyl methacrylate as the inimer

A novel functional inimer 2-(2-bromoisobutyryloxy)ethyl methacrylate(BiBEM) both with the double bond and bromide was designed and synthesised. The branched polystyrene (PS) was prepared by the atom transfer radical polymerisation (ATRP), using BiBEM as inimer (initator) and CuBr complexed with bipyridine as catalysts in toluene at 80°C. The molecular weight and the branching degree of the polystyrene were analysed by using triple detection size-exclusion chromatography (TD-SEC) and the storage modulus in a wide and high-frequency range of polystyrene microrheological properties were studied by the diffusive wave spectroscopy (DWS). By adjusting the ratio of inimer to catalysts, a series of branched polystyrene polymers with different molecular weight and branching degree were obtained. The increase of the BiBEM concentration led to a higher degree of branching, while higher molecular weight and broader molecular weight distribution are accompanied. The branched polystyrene showed low storage modulus and lower chain entanglement compared to linear analogues.