Task-Specific Ionic Liquids-based Polymer: Preparation And Application In The CO₂ Fixation

In this study, the background and progress of CO2 fixation, ionic liquids, nanoparticles and poly(ionic liquid)s, especially CO2 fixation by ionic liquids, are reviewed.Imidazole based ionic liquids with symmetrical ester or hydroxy groups were prepared and their corresponding poly(ionic liquid)s were also synthesized by condensation polymerization for the first time. The structure and properties of poly(ionic liquids) were measured by 1H NMR, GPC, TG, DSC, XRD and SEM. DSC and XRD indicated that polymers are amoprhous, and the glass transition temperature(Tg) ranged from 20~70°C. We also found that the Tg of the poly(ionic liquids) was effcted by cation, anion. TGA analysis demonstrated that polymers have higher decomposed temperature, above 200 oCThe CO2 sorption kinetics of all symmetrical functional ionic liquid and corresponding poly(ionic liquid) was sutdied at 25°C and at low pressure (633.5mmHg) for the first time. The main features of the ionic liquids prepared in this study were that ILs with hydroxyl groups substituent were observed to have larger absorption capacity of CO2, comparison to corresponding symmetrical ester of these ILs, even larger than poly(ionic liquid)s , and faster than that of all reported room temperature ionic liquids. For example, [HHIM]PF6 has a CO2 sorption capacity of 10mol %, it took only 45 minutes to reach absorption equilibrium. This is about 7 times of the capacity of [BMIM]PF6. The study of the relationship between the sorption capacity of CO2 in different structure of poly(ionic liquid)s and functional ionic liquids indicated that all cation, anion and structure can effect CO2 sorption, furthermore, anion is the dominant factor.The functional ionic liquids with symmetrical ester or hydroxy groups were applied as catalysts in the field of cycloaddition of CO2 to epoxides for the first time, indicating that [EEIM]Br was active and selective catalyst for cycloaddition of CO2 to epoxides. The catalytic mechanism of [EEIM]Br was also presumed. Core cross-linked nanoparticles (CCLN) were prepared by a very convenient one-step synthesis through conventional radical copolymerization of the cross-linker EGDMA and phosphorous ionic liquid for the first time. The nanoparticles (NPs) were characterized by 13C-NMR, atomic absorption spectroscopy, TGA, XRD and DLS. TGA analysis shows that the NPs has higher decomposed temperature, more than 265oC, furthermore, it is amoprhous. DLS studies revealed that spherical NPs with the size of about 30-120 nm were prepared when the molar ratio of EGDMA to PIL was 2: 1. The morphology of the cross-linked polymeric particles was observed using scanning electron microscopy (SEM), transparent electron microscopy (TEM) and atomic force microscopy (AFM). Moreover, NPs with core-shell structure could also be observed clearly by TEM. And the shell was much thinner than the core, which indicated that the CCLN was a typical"crew-cut"micelle. Systematic study of the nanoparticles found that the core is PEGDMA, while the shell is PPIL. Furthermore, the catalytic performance of CCLN for the cycloaddition of CO2 to epoxides was studied systemically. It was found that the nanocatalyst was highly active, selective and stable, and could be separated from the products easily and reused without decreasing the catalytic activity obviously. In the optimal conditions, the conversion rate of substrate can reach 99.2% while the selectivity maintained at 100%.