Phase behavior of polymers containing ether groups in carbon dioxide

Polyethers of different composition and chain length were investigated with regard to their solubility in CO2. The nature of the monomeric unit, the degree of polymerization, the endgroup effect, the composition and the temperature significantly influence the solubility and thus the CO2 pressures required for miscibility. In general, it was found that polymers of propylene oxide are more ‘CO2-philic’ than analogs of either ethylene oxide or tetrahydrofuran. The phase behavior of block copolymers of the ethers is influenced by both composition and topology (blocky versus random, block arrangement). It appears that the ether oxygens in polyethers enhance the solubility of such polymers (relative to simple hydrocarbons) through specific interactions with CO2, but only if the ether oxygen is in a readily accessible position.