Preparation of reactive block copolymers and their transformation to hollowed nanostructures

A novel polymeric hollow nanostructure was generated using micellar template method through a three-step procedure. First, the block copolymers were synthesized via ring-opening metathesis polymerization by sequentially adding monomers 7-oxanorborn-5-ene-exo-exo-2,3-dicarboxylic acid dimethyl ester and the mixture of norbornene and 2,3-bis(2-bromoisobutyryloxymethyl)-5-norbornene in chloroform, and also atom transfer radical polymerization of 4-(3-butenyl)styrene was carried out by using the as-obtained block copolymer poly(7-oxanorborn-5-ene-exo,exo-2,3-dicarboxylic acid dimethylester)-block- poly(norbornene-co-2,3-bis(2-bromoisobutyryloxymethyl)-5-norbornene as macroinitiator to afford a graft copolymer bearing poly(4-(3-butenyl)styrene) branch poly(7-oxanorborn-5-ene-exo,exo-2,3-dicarboxylic acid dimethylester)-block-poly(norbornene-co-2,3-bis(2-bromoisobutyryloxymethyl) -5-norbornene)-graft-poly(4-(3-butenyl)styrene). Second, the shell-crosslinked micelles were prepared by ruthenium-mediated ring-closing metathesis of poly(4-(3-butenyl)styrene) branches in intramicelle formed from the copolymers self-assembly spontaneously in toluene. Finally, the hollowed spherical nanoparticles were presented by removing the micellar copolymer backbone through the cleavage of the ester bonds away from the crosslinked network of branches.