Synthesis and self‐assembly of poly(styrene)‐b‐poly(N‐vinylpyrrolidone) amphiphilic diblock copolymers made via a combined ATRP and MADIX approach

Amphiphilic diblock copolymers of polystyrene (PS) and poly( N‐ vinylpyrrolidone) (PNVP) were prepared by a combination of ATRP and MADIX. Well‐defined PS with bromine end group was synthesized by ATRP in bulk at 110 °C using (1‐bromoethyl) benzene as an initiator. The Br‐ end group was then converted to xanthate as verified by 1 H NMR spectroscopy, elemental analysis, and UV‐spectroscopy. PS‐ b ‐PNVP copolymers were produced by MADIX of NVP in bulk at 60 °C using PS‐xanthate as a macro‐chain transfer agent and the kinetics of polymerization were investigated. The structures of PS‐ b ‐PNVP were characterized using GPC and 1 H NMR. Amphiphilic PS‐ b ‐PNVP could form spherical micelles with PS cores and PNVP shells in aqueous solution as confirmed by 1 H NMR and laser light scattering (LLS). The values of critical micelle concentration of PS‐ b ‐PNVP and the average aggregation number of PS‐ b ‐PNVP in the micelles were measured using pyrene as a probe and static LLS, respectively. The aggregation number increases concomitantly with temperature (10–50 °C), but the hydrodynamic radius of the micelles remains almost constant over the same temperature range, which may indicate shell dehydration at a higher temperature.