Shell "locked" nanoassemblies ranging in size from 34 to 78 nm have been prepared from interpolyelectrolyte complexation of block copolymer micelles of poly[(N,N-dimethylacrylamide)-b-(N-acryloylalanine)-b-(N-isopropylacryla mide)] with the homopolymer poly(ar-vinylbenzyl)trimethylammonium chloride above the unimer to micelle phase transition temperature of the block copolymer in water. Of technological significance is the reversibility of the shell cross-linking by addition of 0.4 M NaCl, allowing micelle dissociation below the lower critical solution temperature of the copolymer micelles. Poly(N-acryloylalanine) (AAL) and block copolymers were prepared directly in water via controlled reversible addition fragmentation chain transfer ( RAFT) polymerization utilizing mono- and difunctional poly(N,N-dimethylacrylamide) macroCTAs.