Synthesis of thermo‐responsive poly( N ‐vinylcaprolactam)‐containing block copolymers by cobalt‐mediated radical polymerization

Thermo‐responsive block copolymers based on poly( N ‐vinylcaprolactam) (P N VCL) have been prepared by cobalt‐mediated radical polymerization (CMRP) for the first time. The homopolymerization of N VCL was controlled by bis (acetylacetonato)cobalt(II) and a molecular weight as high as 46,000 g/mol could be reached with a low polydispersity. The polymerization of N VCL was also initiated from a poly(vinyl acetate)‐Co(acac) 2 (PVAc‐Co(acac) 2 ) macroinitiator to yield well‐defined PVAc‐ b ‐P N VCL block copolymers with a low polydispersity ( M w / M n = 1.1) up to high molecular weights ( M n = 87,000 g/mol), which constitutes a significant improvement over other techniques. The amphiphilic PVAc‐ b ‐P N VCL copolymers were hydrolyzed into unprecedented double hydrophilic poly(vinyl alcohol)‐ b ‐P N VCL (PVOH‐ b ‐P N VCL) copolymers and their temperature‐dependent solution behavior was studied by turbidimetry and dynamic light scattering. Finally, the so‐called cobalt‐mediated radical coupling (CMRC) reaction was implemented to PVAc‐ b ‐P N VCL‐Co(acac) 2 precursors to yield novel PVAc‐ b ‐P N VCL‐ b ‐PVAc symmetrical triblock copolymers.