Poly(styrene-co-N-butylmaleimide) macroinitiators by controlled autopolymerization and related block copolymers

Autopolymerization of styrene-N-butylmaleimide mixtures at 125 or 140°C in the presence of a stable nitroxyl radical [2,2,6,6-tetramethylpiperidin-1-yloxyl (TEMPO)] was found to proceed in a pseudoliving manner. Unimolecular initiators, which were originated by trapping self-generated radical species with TEMPO, took part in the process. Under the studied experimental conditions, the TEMPO-controlled autopolymerization with a varying comonomer ratio provided virtually alternating copolymers of narrow molecular weight distributions. The molecular weights of the copolymers increased with conversions. The obtained styrene-N-butylmaleimide copolymers containing TEMPO end groups were used to initiate the polymerization of styrene. The polymerization yielded poly(styrene-co-N-butylmaleimide)-polystyrene block copolymers with various polystyrene chain lengths and narrow molecular weight distributions. The compositions, molecular weights, and molecular weight distributions of the synthesized block copolymers and the initial poly(styrene-co-N-butylmaleimide) precursors were evaluated using nitrogen analysis, gel permeation chromatography, and 1H- and 13C-NMR spectroscopy. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 2378–2385, 1999