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.