Developments in Solid-State NMR Spectroscopy of Polymer Systems

Abstract

Solid-state nuclear magnetic resonance (NMR) has long emerged as a valuable technique for characterizing the molecular structure, conformation, and dynamics of polymer chains in various polymer systems. The principles of the solid-state 13 C NMR cross-polarization experiment are described along with corresponding relaxation measurements. The ensuing recent applications of these techniques to different polymer systems are reviewed, with selected examples that have appeared in the recent literature. All of these applications of solid-state NMR to polymers have one feature in common: the interpretation of spectroscopic observations as related to the structural features and physical properties of the polymer.

Enhanced Protein Extraction from Oilseed Cakes Using Glycerol–Choline Chloride Deep Eutectic Solvents: A Biorefinery Approach

“…The signal at 160–112 ppm in the spectra of precipitates indicates the presence of aromatic carbons, which may come from aromatic side chains of amino acids and from lignin. − Aromatic C signals are more evident in ECPs than RCPs. The carbon signals recorded between 86 and 72 ppm can be assigned to Cα/β-OR of lignin. , In RCP and ECP spectra signals at 65–48 ppm can be assigned to α-carbons in protein and at 56–54 ppm ,, to CH 3 O in lignin. − The carbon signals recorded at 32–10 ppm are associated with the alkyl groups of the side chains of amino acid residues and aliphatic carbons in lignin. − It is worth noting that the intensity of these signals in the RCP and ECP spectra is greater than in the case of BRs and oil cakes. No significant differences were observed in the spectra of the precipitates obtained during extraction at different temperatures.…”

Molecular Characterization of Polymer Networks

“…Through-space correlation methods (e.g., nuclear Overhauser effect spectroscopy (NOESY)) are useful in identifying stereochemistry and describing chain configurations. One advanced NMR method is particularly useful in polymer characterization: diffusion ordered spectroscopy (DOSY) enables the determination of the size and size distribution of polymers that are difficult to characterize via other methods by measuring their distribution of diffusion coefficients, but it only provides an estimated average molecular weight upon calibration. , NMR experiments can be performed in solution or solid-state, depending on sample solubility and information of interest, permitting complete characterization of the precursor strands prior to network formation. − …”

Evaluation of Oolong Teas Using 1H and 13C Solid‐state NMR, Sensory Analysis, and Multivariate Statistics

“…Figure 3 shows the 1 H-13 C CP-MAS spectra of the eight tea samples. Peak assignments were carried out based on the literature 28 and are also indicated in Figure 3. At least 11 peaks can be distinguished in the spectra of Oolong tea.…”

“…[23][24][25][26][27] However, to date, there have been only a few reports on the application of solid-state NMR in the characterization of teas. Martinez-Richa et al 28 obtained 1 H-13 C cross-polarization (CP)-MAS NMR spectra of green and black teas. The carbonyl peak shape and position provided the indicator to distinguish the two teas.…”