FTIR Imaging of Polymeric Materials under High-Pressure Carbon Dioxide

A novel application of FTIR imaging to study polymers subjected to high-pressure CO 2 was demonstrated. FTIR images of polymer blends under high-pressure CO 2 were obtained in situ using a single reflection ATR diamond accessory combined with a high-pressure cell. Two systems, a polystyrene (PS)/poly(vinyl methyl ether (PVME) blend and a poly(ethylene oxide) (PEO)/poly(methyl methacrylate) (PMMA) system, have been studied to demonstrate the feasibility and principles of this new approach. Using this approach, the CO 2 -induced phase separation of an initially homogeneous PS/PVME blend was observed at a CO 2 pressure of 60 bar and temperature of 40 °C. FTIR imaging allowed us to identify formation of distinct domains that are PS- and PVME-rich. The size of these domains was ca. 200 μm. In a second high-pressure imaging experiment, the interfacial region between PEO and PMMA was studied. Sorption of high-pressure CO 2 in both polymers was studied simultaneously. The effect of temperature and pressure on the solubility of CO 2 in PMMA and PEO was demonstrated. The sorption of CO 2 in PEO reduced the melting point of the polymer which facilitated an increase in CO 2 sorption. The successful demonstration of this novel spectroscopic imaging approach under high pressure opens up new possibilities for studying polymeric materials subjected to high-pressure gases and supercritical fluids.