Synthesis and characterization of “Living” star‐shaped poly(N‐vinylcaprolactam) with four arms and carboxylic acid end groups

Poly(N‐vinylcaprolactam) (PNVCL) star‐shaped polymers with four arms and carboxyl end groups were synthesized by reversible addition–fragmentation chain transfer (RAFT) polymerization of N‐vinylcaprolactam (NVCL) employing a tetrafunctional trithiocarbonate as an R‐RAFT agent. The resulting star polymers were characterized using ¹H NMR, FT‐IR, gel permeation chromatography (GPC), and UV–vis. Molecular weight of star polymers were analyzed by GPC and UV–vis being observed that the values obtained were very similar. Furthermore, the thermosensitive behavior of the star polymers was studied in aqueous solution by measuring the lower critical solution temperature by dynamic light scattering. Star‐shaped PNVCL were chain extended with ethyl‐hexyl acrylate (EHA) to yield star PNVCL‐b‐PEHA copolymers with an EHA molar content between 4% and 6% proving the living character of the star‐shaped macroCTA. These star block copolymers form aggregates in aqueous solutions with a hydrodynamic diameter ranged from 170 to 225 nm. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 2156–2165