A novel and facile approach for preparing composite core–shell particles by sequentially initiated grafting polymerization

With the commercially available vulcanized acrylonitrile butadiene rubber (NBR) latex as a model, a facile approach for the preparation of composite core–shell particles was developed. As the first step, UV photoreduction followed by cross-linking/coupling reactions with benzophenone (BP) as the photoinitiator and trimethylpropane triacrylate (TMPTA) as the accelerator were carried out in order to attach dormant semi-pinacol groups to the surface of the NBR particles (NBR–SP). The second step, carried out under heating, involved the grafting of styrene (St) which was induced from the particle surface by bond breaking of NBR–SP and propagation towards the center of the particles. The grafting efficiency could be kept at a high level, i.e. approx. 90%, and the grafting yield increased with time (could reach up to 140%). Finally, by adding acrylamide (AM) or N-vinyl pyrrolidone (NVP) as a second monomer under heating, a composite core–shell particle could be prepared.