High-pressure phase behavior and FT-IR study of poly(methyl methacrylate) plus ethanol systems with addition of supercritical CO2

The phase equilibria of carbon dioxide (CO(2)) + poly(methyl methacrylate) (PMMA; Mw = 15 k) + ethanol ternary systems were measured at temperatures ranging from 293.3 to 359.7 K and pressures up to 14.1 MPa. In order to determine the phase boundary, we observed the cloud points and bubble points by using a variable volume view cell. Furthermore, the dissolution process of PMMA in CO(2)-expanded ethanol was studied using FTIR spectroscopy. Although both CO(2) and ethanol are nonsolvents for PMMA at 303 K, PMMA dissolved in CO(2)-expanded ethanol. The noticeable band was carbonyl stretching band for PMMA. No peak shifts and/or no contributions were obtained for PMMA in pure ethanol at 303 K, because ethanol is nonsolvent for PMMA. With addition of CO(2) in the mixture of PMMA and ethanol, the carbonyl stretching band of PMMA has a weak contribution at lower wave numbers. It is indicated that a strong interaction between PMMA and ethanol via hydrogen bonding exists.