Pluronic L121, BMIM BF4 and PEG-400 comparison to identify the best solvent for CO2 sorption

The triblock copolymer L121 [poly(ethylene glycol)5-block-poly(propylene glycol)68-block-poly(ethylene glycol)5], the room temperature ionic liquid BMIM BF4 (1-butyl-3-methylimidazolium tetrafluoroborate) and the polymer PEG-400 (polyethylene glycol-400) have been compared in their liquid state to test their sorption capability of CO2 by exposure to high-pressure gas for 3 h in a controlled system. The presence of the gas in the studied systems has been determined at atmospheric pressure in the temperature range 288.15–313.15 K by using near-infrared (NIR) spectroscopy. The CO2 sorption in BMIM BF4 and PEG-400 was very small and detectable up to 293.15 K, only L121 showed the CO2 typical bands in the NIR region of the spectra up to 313.15 K, thus a linear correlation can be obtained by plotting the CO2 absorbance of those bands as a function of temperature. The effect induced by temperature on the swelling degree of L121 copolymer has also been investigated.