Communication: A new class of polymer (nanocomposite) materials of di-and triblock polymers of polystyrene, poly(butyl acrylate) and poly(acetoacetoxyethyl methacrylate) with a core-shell particle morphology and controlled molecular weight distribution were prepared via emulsion polymerization in the presence of a reversible addition/fragmentation chain transfer agent. The film properties of these blocks are far superior to the conventional blend of the two polymers even after crosslinking with 1,6-hexadiamine.