Poly(N-acryloxysuccinimide) (PNAS) and poly(N-acryloxysuccinimide-co-N-vinylpyrrolidone) (P(NAS-co-NVP)) of adjustable molecular weights and narrow polydispersities were prepared by nitroxide-mediated polymerization (NMP) in N,N-dimethylformamide in the presence of free SG1 (N-tert-butyl-N-1-diethylphosphono-)2,2-dimethylpropyl) nitroxide), with MAMA-SG 1 (N-(2-methylpropyl)-N-(1-diethylphosphono-2,2-dimethylpropyl)-O-(2-carbo xylprop-2-yl)hydroxylamine) alkoxyamine as initiator. The reactivity ratios of NAS and NVP were determined to be r(NAS) = 0.12 and r(NVP) = 0, indicating a strong alternating tendency for the P(NAS-co-NVP) copolymer. NAS/NVP copolymerization was then performed from a SG1-functionalized poly(D,L-lactice) (PLA-SG1) macro-alkoxyamine as initiator, leading to the corresponding PLA-b-P(NAS-co-NVP) block copolymer, with similar NAS and NVP reactivity ratios as mentioned above. The copolymer was used as a surface modifier for the PLA diafiltration and nanoprecipitation processes to achieve nanoparticles in the range of 450 and 150 nm, respectively. The presence of the functional/hydrophilic P(NAS-co-NVP) block, and particularly the N-succinimidyl (NS) ester moieties at the particle surface, was evidenced by ethanolamine derivatization and zeta potential measurements. (C) 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 49: 13411350, 2011