Non-fluorous polymers with very high solubility in supercritical CO2 down to low pressures

Liquid and supercritical carbon dioxide have attracted much interest as env ironmentally benign solvents(1), but their practical use has been limited b y the need for high CO2 pressures to dissolve even small amounts of polar, amphiphilic, organometallic, or high-molecular-mass compounds(2-4). So-call ed 'CO2-philes' efficiently transport insoluble or poorly soluble materials into CO2 solvent, resulting in the development of a broad range of CO2 bas ed processes, including homogeneous and heterogeneous polymerization, extra ction of proteins and metals, and homogeneous catalysis(5-11). But as the m ost effective CO2-philes are expensive fluorocarbons, such as poly(perfluor oether), the commercialization of otherwise promising CO2-based processes h as met with only limited success. Here we show that copolymers can act as e fficient, non-fluorous CO2-philes if their constituent monomers are chosen to optimize the balance between the enthalpy and entropy of solute-copolyme r and copolymer-copolymer interactions. Guided by heuristic rules regarding these interactions, we have used inexpensive propylene and CO2 to synthesi ze a series of poly(ether-carbonate) copolymers that readily dissolve in CO 2 at low pressures. Even though non-fluorous polymers are generally assumed to be CO2-phobic, we expect that our design principles can be used to crea te a wide range of non-fluorous CO2-philes from low-cost raw materials, thu s rendering a variety of CO2-based processes economically favourable, parti cularly in cases where recycling of CO2-philes is difficult.