Synthesis of poly[2-(perfluorooctyl)ethyl acrylate-co-poly(ethylene glycol) methacrylate] and its control of enzyme activity in supercritical carbon dioxide

Abstract

Poly[2-(perfluorooctyl)ethyl acrylate-co-poly(ethylene glycol) methacrylate], P(POA-co-PEGm) was prepared as a new surfactant for scCO2. The random copolymer was obtained by the radical polymerization of 2-(perfluorooctyl)ethyl acrylate (POA) and poly(ethylene glycol) methacrylate (PEGm) in DMF. The molar ratio of the POA and PEGm units in the copolymer was POA/PEGm = 0.972/0.028 by 1H NMR. The molecular weight and molecular weight distribution were estimated by size exclusion chromatography to be Mn = 133,000 and Mw/Mn = 8.25, respectively. It was suggested that the copolymer formed micellar aggregates with the cores of the PEGm chains in scCO2, based on the analyses of the copolymer in hexafluorobenzene by 1H NMR and dynamic light scattering. The copolymer was soluble in scCO2 and had a cloud point at a much higher pressure than the critical pressure. It was found that the copolymer solubilized CO2-insoluble proteins such as bovine serum albumin and subtilisin Carlsberg in scCO2. The solubility of the copolymer was not influenced by the presence of the proteins; however, the solubility decreased in the presence of a small amount of water along with the protein. The activity of the subtilisin slightly decreased when only placed in scCO2, whereas a marked decrease in the activity was observed for the subtilisin in the presence of the copolymer in scCO2. The subtilisin activity decreased as the CO2 pressure increased.