Quantum Chemical Calculation on 1H NMR Chemical Shifts of PMMA/PVPh Blends

Prediction of chemical shifts using quantum chemical calculation is helpful for assigning nuclear magnetic resonance (NMR) spectra, and very important in structure determination. In this paper, we calculated H-1 chemical shifts (delta H) of poly (methyl methacrylate) (PMMA), poly (4-vinyl phenol) (PVPh) and their polymer blends. Density functional theory (DFT) was used to compute delta H of hydroxyl groups (OH) for both PVPh homopolymer and PMMA/PVPh polymer blends. The calculated values for delta H of OH groups with or without forming hydrogen bonds agreed reasonably well with the experimental values. It was found that the delta H of OH groups moved downfield when they formed hydrogen bonds with both other OH groups and carbonyl groups (C=O). The simulated solid state H-1 NMR spectra based on the B3LYP // GIAO method yielded results for the PMMA, PVPh and PMMA/PVPh, showed excellent agreement with the experimental results. It indicates that the H-1 NMR spectra are influenced by the main-chain conformations and the hydrogen bond types.