Preparation of Thermo-Responsive Poly(ionic liquid)s-Based Nanogels via One-Step Cross-Linking Copolymerization.

Yong Zuo,Jingjiang Liu,Jing Zhang,Rongmin Wang,Yubing Xiong

doi:10.3390/molecules200917378

Abstract

In this study, thermo-responsive polymeric nanogels were facilely prepared via one-step cross-linking copolymerization of ethylene glycol dimethacrylate/divinylbenzene and ionic liquid (IL)-based monomers, 1,n-dialkyl-3,3′-bis-1-vinyl imidazolium bromides ([CnVIm]Br; n = 6, 8, 12) in selective solvents. The results revealed that stable and blue opalescent biimidazolium (BIm)-based nanogel solutions could be obtained without any precipitation when the copolymerizations were conducted in methanol. Most importantly, these novel nanogels were thermo-response, and could reversibly transform to precipitation in methanol with temperature changes. Turbidity analysis and dynamic light scatting (DLS) measurement illustrated that PIL-based nanogel solutions presented the phase transform with upper critical solution temperature (UCST) in the range of 5–25 °C. The nanogels were characterized using Fourier transform infrared (FTIR), thermogravimetric analyses (TGA), and scanning electron microscopy (SEM). In addition, BIm-based nanogels could also be used as highly active catalysts in the cycloaddition reaction of CO2 and epoxides. As a result, our attributes build a robust platform suitable for the preparation of polymeric nanomaterials, as well as CO2 conversion.

Highlights

In the past few decades, ionic liquids (IL) have garnered considerable attention in a variety of fields because of their excellent properties, such as vanishingly low vapor pressure, non-flammable, excellent chemical and thermal stability in the liquid state, polarity tunability, high ionic conductivity, wide electrochemical windows, etc. [1,2,3,4,5,6]
The results demonstrated that all these BIm-based monomers were synthesized with acceptable yield
1H-NMR spectra of these monomers were conducted in different deuterium solvents

Summary

Introduction

In the past few decades, ionic liquids (IL) have garnered considerable attention in a variety of fields because of their excellent properties, such as vanishingly low vapor pressure, non-flammable, excellent chemical and thermal stability in the liquid state, polarity tunability, high ionic conductivity, wide electrochemical windows, etc. [1,2,3,4,5,6]. Several latest reviews have summarized the recent development on the design of ILs/PILs with thermo-responsive phase behaviors in water and organic solvents [17,18,19] As cited in these reviews, some interesting thermo-responsive IL/PIL systems were masterly explored. Thermo-responsive nanogels could be obtained for the first time via the copolymerization of the geminal dicationic, 1,4-butanediyl-3,3′-bis-1-vinyl imidazolium halides, and the cross-linkers described previously under the same conditions [28] These novel PIL-based thermo-responsive nanogels can reversibly form precipitates or macrogels in methanol with the temperature changing in the range of −15 to 25 °C. It is highly desired to get insight into the rules of the thermo-responsive behavior, and develop a simple approach for the preparation of thermo-responsive nanogels based PIL To achieve this goal, we will elucidate the relationship between the thermo-response of nanogels and the structure of ionic liquid-based monomers in this paper

Synthesis of Biimidazolium Salt-Based Monomers

Experimental Section

Conclusions