Hyperbranched Nanomolecules: Regular Polystyrene Dendrigrafts

Abstract

Arborescent graft polystyrenes were prepared by the “graft on graft” technique, involving the iterative grafting of end-functional polymer chains onto reactive polymer backbones. The grafts and the reactive backbone building blocks were synthesized individually by living polymerization techniques. The first-generation comb polymers were obtained by the coupling reaction of living α-acetal polystyryllithium onto poly(chloroethyl vinyl ether) PCEVE chains of controlled n . Initiation from acetal termini of polystyrene branches of a new living cationic polymerization of chloroethyl vinyl ether (CEVE) allowed one to prepare the corresponding comb copolymers with polystyrene- b -poly(chloroethyl vinyl ether) branches. Hyperbranched polystyrenes were finally obtained by grafting a second amount of polystyryllithium onto the CEVE units of poly(CEVE) external blocks. Nanomolecules of narrow molar masses distribution, branching functionalities up to 35 000, and molar masses over 10 8 g/mol were obtained by this method. By varying n of the different elementary building blocks, various polystyrene dendrigrafts were prepared, demonstrating the possibility to control the core−shell parameters of these macromolecular objects. The solution properties and the characteristic chain parameters ([η], R g, R h,) of the hyper-branched polystyrene macromolecules were determined and compared with literature data.