Supercritical CO₂ impregnation process applied to polymer samples preparation for dynamic nuclear polarization...

Area of Science:

• Materials Science
• Analytical Chemistry
• Biophysics

Background:

• Dynamic Nuclear Polarization (DNP) enhances NMR sensitivity.
• Solid-state NMR (ssNMR) requires efficient sample preparation for DNP.
• Traditional methods for DNP sample preparation can be time-consuming or inefficient.

Purpose of the Study:

• To investigate supercritical CO2 (scCO2) as a novel method for impregnating polymers with paramagnetic polarizing agents.
• To prepare polymer samples for DNP-enhanced ssNMR experiments.
• To evaluate the efficiency and versatility of scCO2 impregnation for DNP ssNMR.

Main Methods:

• Utilized supercritical CO2 (scCO2) to impregnate polystyrene samples with a bTbK polarizing agent (bis-TEMPO-bisketal).
• Conducted DNP-enhanced 1H → 13C cross-polarization (CP) magic-angle spinning (MAS) ssNMR experiments.
• Recorded spectra at 9.4 T and approximately 100 K.

Main Results:

• Achieved substantial DNP signal enhancements on the prepared polystyrene samples.
• Observed maximum signal enhancements of up to 8.
• Demonstrated signal enhancements comparable to or exceeding those from previous sample preparation methods.

Conclusions:

• Supercritical CO2 (scCO2) impregnation is a viable and efficient method for preparing polymer samples for DNP ssNMR.
• This technique shows potential as a versatile approach for DNP ssNMR sample preparation.
• The scCO2 method offers a promising alternative for researchers in materials science and biophysics.