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

Abstract

In this paper, double hydrophilic ionic liquid block copolymers (ILBCs), poly(N-isopropylacrylamide)-block-poly[1-methyl-3-(2-methacryloyloxy propylimidazolium bromine)] (PNIPAM-b-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 chromatography (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 (CF₃SO₂)₂N^--, the micellization of self-assembling PNIPAM-b-PMMPImB was induced to form a core--shell structure containing the core with hydrophilic PMMPIm-(CF₃SO₂)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.

Keywords

ionic liquid block copolymer (ILBC) / self-assembly / micelles / stimulus-responsive polymer nanoparticle

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Acknowledgements

We acknowledge the financial support from the National Natural Science Foundation of China (Grant Nos. 51103035 and 51403055).

RIGHTS & PERMISSIONS

2014 Higher Education Press and Springer-Verlag Berlin Heidelberg