Synthesis and self-assembly of thermo/pH-responsive double hydrophilic brush–coil copolymer with poly(l-glutamic acid) side chains

Abstract

We report on the synthesis and self-assembly behavior of a well-defined double hydrophilic brush–coil copolymer with poly(N-isopropylacrylamide)-b-poly(glycidly methacrylate) (PNIPAM-b-PGMA) as backbone and poly(l-glutamic acid) (PLGA) as brush. The PNIPAM-b-PGMA was firstly prepared by the sequential reversible addition–fragmentation chain transfer polymerization of N-isopropylacrylamide and glycidly methacrylate. The obtained diblock copolymer was reacted with ethylenediamine (EDA) yielding the aminated macroinitiator (PNIPAM-b-PGMA-EDA), which was then used to initiate ring-opening polymerization of γ-benzyl-l-glutamate-N-carboxyanhydride (BLG-NCA) to give PNIPAM-b-(PGMA-g-PBLG) copolymer. After the deprotection of benzyl groups on PBLG, double hydrophilic brush–coil copolymer, PNIPAM-b-(PGMA-g-PLGA), was obtained. The thermo- and pH-responsive micellization behaviors of PNIPAM-b-(PGMA-g-PLGA) in aqueous solution were investigated by fluorescence spectroscopy, 1H NMR, dynamic light scattering, scanning electron microscopy, and circular dichroism. It can self-assemble into PNIPAM-core micelles at pH 10 and elevated temperature and PLGA-core micelles at pH 4 and room temperature. Such brush–coil copolymers have the potential applications as biomedical and intelligent materials.