Atom transfer radical polymerization of styrenic ionic liquid monomers and carbon dioxide absorption of the polymerized ionic liquids

Polymeric forms of ionic liquids have many potential applications because of their high thermal stability and ionic nature. Two ionic liquid monomers, 1-(4vinylbenzyl)-3-butyl imidazolium tetrafluoroborate (VBIT) and 1-(4-vinylbenzyl)-3-butyl imidazolium hexafluorophosphate (VBIH), were synthesized through the quaternization of N-butylimidazole with 4-vinylbenzylchloride and a subsequent anion-exchange reaction with sodium tetrafluoroborate or potassium hexafluorophosphate. Copper-mediated atom transfer radical polymerization was used to polymerize VBIT and VBIH. The effects of various initiator/catalyst systems, monomer concentrations, solvent polarities, and reaction temperatures on the Polymerization were examined. The polymerization was well controlled and exhibited living characteristics when CuBr/1,1,4,7,10,10-hexamethyltriethylenetetramine or CuBr/2,2'-bipyridine was used as the catalyst and ethyl 2-bromoisobutyrate was used as the initiator. Characterizations by thermogravimetric analysis, differential scanning calorimetry, and X-ray diffraction showed that the resulting VBIT polymer, poly[1-(4-vinylbenzyl)-3-butyl imidazolium tetrafluoroborate] (PVBIT), was amorphous and had excellent thermal stability, with a glass-transition temperature of 84 degrees C. The polymerized ionic liquids could absorb CO2 as ionic liquids: PVBIT absorbed 0.30% (w/w) CO2 at room temperature and 0.78 atm. (c) 2005 Wiley Periodicals, Inc.