Crosslinked phosphate esters thicken n‐butane and propane, but not ethane or CO 2

The efficacy of crosslinked phosphate esters for thickening light liquid alkanes and CO 2 was determined. A 90% diester—10% monoester mixture of phosphate esters with an equimolar mixture of butyl, pentyl, and hexyl moieties induced viscosity increases of at least three orders of magnitude in compressed liquid n‐butane and propane. This thickening occurred several hours after 0.5 vol% phosphate esters and 0.5 vol% Fe 3+ crosslinking solution were mixed with the high‐pressure liquid alkane. Because the crosslinked phosphate ester (CPE) network remained dissolved in propane and n‐butane, viscosity enhancement occurred. However, when combined with liquid ethane or CO 2 under the same conditions, the CPE immediately precipitated as a light brown solid. Therefore, a novel phosphate ester based on an oxygenated hydrocarbon group derived from diethylene glycol ethyl ether was synthesized to generate a more CO 2 ‐philic CPE network that would remain dissolved in CO 2 . However, the corresponding CPE precipitated in CO 2 .