FTIR imaging of polymeric materials under high-pressure carbon dioxide

A novel application of FTIR imaging to study polymers subjected to high-pressure CO2 was demonstrated. FTIR images of polymer blends under high-pressure CO2 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 CO2-induced phase separation of an initially homogeneous PS/PVME blend was observed at a CO2 pressure of 60 bar and temperature of 40 degreesC. FTIR imaging allowed us to identify formation of distinct domains that are PS- and PVME-rich. The size of these domains was ca. 200 mum. In a second high-pressure imaging experiment, the interfacial region between PEO and PMMA was studied. Sorption of high-pressure CO2 in both polymers was studied simultaneously. The effect of temperature and pressure on the solubility of CO2 in PMMA and PEO was demonstrated. The sorption of CO2 in PEO reduced the melting point of the polymer which facilitated an increase in CO2 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.