Hydrogen bonding induced UCST phase transition of poly(ionic liquid)-based nanogels

- IL monomers with hydroxyl and carboxyl groups are prepared.
- Functional nanogels are obtained via one-step ternary copolymerization.
- PIL-based nanogels are thermoresponsive.
- UCST of PIL-based nanogel can be tuned via the feed ratio.
- Reversible nanogel-macrogel transition can be achieved with high [VCMIm]Cl feed.

In this study, novel thermo-responsive nanogels were facilely fabricated via ternary cross-linking copolymerization of ionic liquid (IL)-based monomers and cross-linker in methanol. To achieve the thermo-responsive performance of nanogels, monomers with hydroxyl or carboxyl group which can contribute to hydrogen (H)-bonding interaction is the key point of this strategy. The thermo-responsive behavior of poly(ionic liquid)s (PIL)-based nanogels were testified using dynamic light scattering (DLS), turbidimetric method, and differential scanning calorimetry (DSC) measurements. The results demonstrated that these novel nanogels presented reversible upper critical solution temperature (UCST) phase transition with the temperature changing. And their UCSTs could be tuned via the feed ratio of IL-based monomers and cross-linker. The nanogels were also measured using scanning electronic microscopy (SEM), thermo-gravimetric analyses (TGA) and Fourier transform infrared spectroscopy (FT-IR) techniques. In addition, a possible mechanism of thermo-responsive performance was suggested based on the above results. As a result, our findings provide an efficient and applicable platform for the fabrication of thermo-responsive polymeric nanomaterials.

Thermo-responsive nanogels based on poly(ionic liquid)s were facilely fabricated via one-step cross-linking copolymerization of carboxyl- or hydroxyl-contained ionic liquid monomers in methanol.349