AI Article Synopsis
- High-pressure electron paramagnetic resonance (EPR) was used to measure the translational diffusion coefficients of TEMPONE spin probe in poly(D,L-lactide) (PDLLA) swollen in supercritical CO, utilizing both macroscopic and microscopic scales.
- The measured diffusion coefficients were similar across methods, ranging from 5-10 × 10 m/s at temperatures of 40-60 °C and pressures of 8-10 MPa, indicating homogeneity of the swollen PDLLA on a nanometer scale.
- However, the TEMPONE spin probe displayed unexpectedly high rotational mobility, and supercritical chromatography revealed that only the beginning of the impregnation process showed significant differences between powder and bulk polymer samples.
Article Abstract
High-pressure electron paramagnetic resonance (EPR) was used to measure translational diffusion coefficients (D) of a TEMPONE spin probe in poly(D,L-lactide) (PDLLA) and swollen in supercritical CO. D was measured on two scales: macroscopic scale (>1 μm), by measuring spin probe uptake by the sample; and microscopic scale (<10 nm), by using concentration-dependent spectrum broadening. Both methods yield similar translational diffusion coefficients (in the range 5-10 × 10 m/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 (τ = 6 × 10 s) than expected, based on its D. 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.
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| http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8466873 | PMC |
| http://dx.doi.org/10.3390/polym13183059 | DOI Listing |
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Article Synopsis
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