Insight into the role of intermolecular interactions on the enhanced solubility of fluorinated epoxide oligomers in supercritical CO2

Abstract

A prominent enhancement in solubility of epoxide oligomers in supercritical CO₂ (scCO₂) was definitively accomplished via fluorination. The fluorinated epoxide oligomers (FEO) exhibited incredibly low transition pressure (P_T) as compared with a library of other epoxide oligomers. For determining the nature of the observed special affinity of the FEO to CO₂, the detailed solvation behaviors of 14 epoxide oligomers in gaseous and supercritical CO₂ were investigated using a high-pressure in situ ATR FTIR system as the pressure increased from 0.1 to 40.0 MPa. The key role of the intermolecular interactions on the enhanced solubility of the FEO in scCO₂ was established and the major factors impacting the molecular interplay between the epoxide oligomers and CO₂ were systematically evaluated. We attribute the uniquely enhanced solubility of the FEO in scCO₂ to the synergistic effects of the increased special attraction between the FEO and CO₂, the decreased self-interaction among the FEO and the excellent accessibility of the FEO to CO₂. Since the FEO are suggested to be the most soluble species in scCO₂, we optimistically believe that the FEO may act as the ideal solubilizing chain after being transplanted or grafted into other targeted molecules and thus can be employed in developing a series of novel fluorinated monomers, ligands/complexes/catalysts and surfactants in a scCO₂ system.