Hyperbranched nanomolecules: Regular polystyrene dendrigrafts

Arborescent graft polystyrenes were prepared by the "graft on graft" techni que, 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. T he first-generation comb polymers were obtained by the coupling reaction of living alpha -acetal polystyryllithium onto poly(chloroethyl vinyl ether) PCEVE chains of controlled DPn. Initiation from acetal termini of polystyre ne branches of a new living cationic polymerization of chloroethyl vinyl et her (CEVE) allowed one to prepare the corresponding comb copolymers with po lystyrene-b-poly(chloroethyl vinyl ether) branches. Hyperbranched polystyre nes 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 mola r masses over 10(8) g/mol were obtained by this method. By varying DPn of t he different elementary building blocks, various polystyrene dendrigrafts w ere prepared, demonstrating the possibility to control the core-shell param eters of these macromolecular objects. The solution properties and the char acteristic chain parameters ([eta], R-g, R-h,) of the hyper-branched polyst yrene macromolecules were determined and compared with literature data.