HYPERBRANCHED NANOMOLECULES: REGULAR POLYSTYRENE DENDRIGRAFTS

Arborescent graft polystyrenes were prepared by the “graft on graft” technique, involvingthe iterative grafting of end-functional polymer chains onto reactive polymer backbones. The grafts andthe reactive backbone building blocks were synthesized individually by living polymerization techniques.The first-generation comb polymers were obtained by the coupling reaction of living R-acetal polystyryllithiumonto poly(chloroethyl vinyl ether) PCEVE chains of controlled DPn. Initiation from acetaltermini 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 polystyryllithiumonto the CEVE units of poly(CEVE) external blocks. Nanomolecules of narrow molar massesdistribution, branching functionalities up to 35 000, and molar masses over 108 g/mol were obtained bythis method. By varying DPn of the different elementary building blocks, various polystyrene dendrigraftswere prepared, demonstrating the possibility to control the core-shell parameters of thesemacromolecular objects. The solution properties and the characteristic chain parameters ([è], Rg, Rh,) ofthe hyper-branched polystyrene macromolecules were determined and compared with literature data.