Synthesis and self-assembly of temperature and anion double responsive ionic liquid block copolymers

摘要

In this paper, double hydrophilic ionic liquid block copolymers (ILBCs), poly(N-isopropylacrylamide)-block-poly[1-methyl-3-(2-methacryloyloxy propylimidazo-lium bromine)] (PNIPAM-fo-PMMPImB), were polymerized by two-step reversible addition-fragmentation chain transfer (RAFT) process. The composition and molecular weight distributions of ILBCs were characterized using ~1HNMR and gel permeation chromato-graphy (GPC). The self-assembly and temperature- and anion-responsive behaviors of ILBCs were investigated by UV-Vis spectroscopy, TEM and dynamic light scattering (DLS). With increasing the concentration of (CF_3SO_2)_2N~-, the micellization of self-assembling PNIPAM-fo-PMMPImB was induced to form a core-shell structure containing the core with hydrophilic PMMPIm-(CF_3SO_2)_2N~- surrounded by the shell of PNIPAM via the anion-responsive properties of ILBCs. However, upon temperature increasing, PNIPAM-b-PMMPImB formed the micelles composing of PNIPAM core and PMMPImB shell. The ionic liquid segment with strong hydrophilic property enhanced the hydrogen bonding interaction which expanded the temperature range of phase transition and increased the lower critical solution temperature (LCST) of the system. These results indicate that ILBCs prepared in this paper have excellent temperature and anion double responsive properties, and may be applied as a kind of potential environmental responsive polymer nanoparticles.