Solute Diffusion into Polymer Swollen by Supercritical CO<sub>2</sub> by High-Pressure Electron Paramagnetic Resonance Spectroscopy and Chromatography
Oleg I. Gromov,
Mikhail O. Kostenko,
Alexander V. Petrunin,
Anastasia A. Popova,
Olga O. Parenago,
Nikita V. Minaev,
Elena N. Golubeva,
Mikhail Ya. Melnikov
Affiliations
Oleg I. Gromov
Faculty of Chemistry, Lomonosov Moscow State University, Leninskiye Gory, 1-3, 119991 Moscow, Russia
Mikhail O. Kostenko
Kurnakov Institute of General and Inorganic Chemistry of the Russian Academy of Sciences, Leninsky Prosp. 31, 119991 Moscow, Russia
Alexander V. Petrunin
Institute of Physical Chemistry, RWTH Aachen University, 52056 Aachen, Germany
Anastasia A. Popova
Faculty of Chemistry, Lomonosov Moscow State University, Leninskiye Gory, 1-3, 119991 Moscow, Russia
Olga O. Parenago
Faculty of Chemistry, Lomonosov Moscow State University, Leninskiye Gory, 1-3, 119991 Moscow, Russia
Nikita V. Minaev
Federal Scientific Research Centre “Crystallography and Photonics” RAS, Institute of Photon Technologies, Pionerskaya Str. 2, Troitsk, 108840 Moscow, Russia
Elena N. Golubeva
Faculty of Chemistry, Lomonosov Moscow State University, Leninskiye Gory, 1-3, 119991 Moscow, Russia
Mikhail Ya. Melnikov
Faculty of Chemistry, Lomonosov Moscow State University, Leninskiye Gory, 1-3, 119991 Moscow, Russia
High-pressure electron paramagnetic resonance (EPR) was used to measure translational diffusion coefficients (Dtr) of a TEMPONE spin probe in poly(D,L-lactide) (PDLLA) and swollen in supercritical CO2. Dtr was measured on two scales: macroscopic scale (>1 μm), by measuring spin probe uptake by the sample; and microscopic scale (−12 m2/s at 40–60 °C and 8–10 MPa). Swollen PDLLA was found to be homogeneous on the nanometer scale, although the TEMPONE spin probe in the polymer exhibited higher rotational mobility (τcorr = 6 × 10−11 s) than expected, based on its Dtr. To measure distribution coefficients of the solute between the swollen polymer and the supercritical medium, supercritical chromatography with sampling directly from the high-pressure vessel was used. A distinct difference between powder and bulk polymer samples was only observed at the start of the impregnation process.
