Nitroxide-mediated radical copolymerization of 2-vinylpyridine (2VP) with acrylonitrile (AN) at various mole fractions of 2VP in the feed at 125'C was studied. An alkoxyamine containing the diethoxyphosphoryl group (MAMA-SG1) or a two-component system of 2,2'-azobis(isobutyronitrile) or dibenzoyl peroxide in combination with nitroxyl radicals TEMPO were used for the initiation; in addition, spontaneous thermal radical copolymerization of both the comonomers was performed in the presence of a nitroxide. The obtained nitroxide-terminated 2VP-AN copolymers showed a low polydispersity (M-omega/M-n similar to 1.2). They initiated polymerization of styrene (S) giving poly(2VP-co-AN)-block-polyS diblock copolymers; however, in dependence on the used macroinitiator, the resulting products might be markedly contaminated with inactive polymer chains. On the other hand, the 2VP-AN copolymerization, which was initiated at 125 degrees C with a TEMPOterminated polyS, proved to be an efficient synthetic route for the preparation of diblock copolymers comprising blocks of polyS and poly(2VP-co-AN). The synthesized copolymers were characterized by NMR spectroscopy and size-exclusion chromatography. (c) 2007 Wiley Periodicals, Inc.