Synthesis and characterization of hetero‐arm star copolymers

Abstract

Abstract Hetero‐arm star copolymers are constituted of a central core carrying branches of two kinds. The two‐stage synthesis of such polymer species involves an arm‐first step and a core‐first step: A linear anionic living polystyrene precursor was used to initiate the polymerization of a small amount of divinylbenzene, yielding star‐shaped polystyrene bearing living sites inside the cores; in a second stage these sites were used to initiate the polymerization of another monomer — butyl methacrylate —, more electrophilic than styrene. This second step results in the formation of a new set of branches originating from the same polydivinylbenzene cores. The star polystyrenes, and the hetero‐arm star copolymers were characterized adequately, and their molecular weights were found to be in satisfactory agreement with expectation. The presence of some remaining linear precursor in the star polymer samples is discussed thoroughly on the basis of a detailed computerized analysis of the size exclusion chromatograms of both the star polystyrene samples and the hetero‐arm star copolymers.