Synthesis and characterization of PNIPAM‐<i>b</i>‐(PEA‐<i>g</i>‐PDEA) double hydrophilic graft copolymer

Abstract

Abstract A series of well‐defined double hydrophilic graft copolymers, consisting of poly( N ‐isopropylacrylamide)‐ b ‐poly(ethyl acrylate) (PNIPAM‐ b ‐PEA) backbone and poly(2‐(diethylamino)ethyl methacrylate) (PDEA) side chains, were synthesized by successive atom transfer radical polymerization (ATRP). The backbone was firstly prepared by sequential ATRP of N ‐isopropylacrylamide and 2‐hydroxyethyl acrylate at 25 °C using CuCl/tris(2‐(dimethylamino)ethyl)amine as catalytic system. The obtained diblock copolymer was transformed into macroinitiator by reacting with 2‐chloropropionyl chloride. Next, grafting‐from strategy was employed for the synthesis of poly( N ‐isopropylacrylamide)‐ b ‐[poly(ethyl acrylate)‐ g ‐poly(2‐(diethylamino)ethyl methacrylate)] (PNIPAM‐ b ‐(PEA‐ g ‐PDEA)) double hydrophilic graft copolymer. ATRP of 2‐(diethylamino)ethyl methacrylate was initiated by the macroinitiator at 40 °C using CuCl/hexamethyldiethylenetriamine as catalytic system. The molecular weight distributions of double hydrophilic graft copolymers kept narrow. Thermo‐ and pH‐responsive micellization behaviors were investigated by fluorescence spectroscopy, 1 H NMR, dynamic light scattering, and transmission electron microscopy. Unimolecular micelles with PNIPAM‐core formed in acidic environment (pH = 2) with elevated temperature (≥32 °C); whereas, the aggregates turned into vesicles in basic surroundings (pH ≥ 7.2) at room temperature. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5638–5651, 2008