Synthesis of Polystyrene-Based Hyperbranched Polymers by Thiol-Yne Chemistry: A Detailed Investigation

This contribution reports on the preparation of hyperbranched polymers via thiol-yne photopolymerization of macromolecules bearing a thiol group at one of their chain end and an alkyne moiety at the other. These thiol/yne macromonomers were produced by the reversible addition-fragmentation chain transfer (RAFT) polymerization of styrene mediated by an alkyne-containing chain transfer agent, followed by the aminolysis of the trithiocarbonate groups into thiol moieties. The first part of this report concentrates on studying the effects upon the thiol-yne photopolymerization process caused by the variation of several experimental conditions, such as the size of the thiol/yne macromonomer utilized, the amount of photoinitiator added, or the initial concentration of macromonomer used. Among the various parameters investigated, the latter was demonstrated to be the leading factor that contributes to the final size of the hyperbranched structures. The second part of this article discusses the multidetector size-exclusion chromatography (SEC) analysis of the materials obtained by thiol-yne photopolymerization. This analytical technique allows the molecular weight of the hyperbranched polymers to be determined and the hyperbranched topology to be confirmed, as highlighted by the increased density of the materials compared to that of linear equivalents of the same chemical composition and identical molar masses.