Impregnation of Polycarbonate by Paramagnetic Probe 2,2,6,6-Tetramethyl-4-Hydroxy-Piperidine-1-Oxyl (TEMPOL) in Supercritical CO2

Abstract

The aim of the research was to test the advantages of spin probe electron paramagnetic resonance approach in studying polymers impregnation with organic molecules in supercritical CO₂ (scCO₂) The impregnation of bisphenol A polycarbonate with the spin probe TEMPOL was carried out at 307–343 K and 11.6–35 MPa. The mean and local concentrations of the spin probe in the polymer were evaluated. An increase in temperature and pressure resulted in a more even distribution of the dopant in the polymer matrix. It was observed that, at 307 K and 19.6 MPa, the spin probe was located only near the surface of the sample. Local mobility of the spin probe molecules was found to be similar in polycarbonate films impregnated in scCO₂ and cast from dichloroethane solution. It was shown that changes in the structure of the surface and bulk of the polymer detected by the atomic force and optical polarization microscopy are not directly related with the distribution of the dopant molecules and their average content in the polymer.