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

摘要

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 ~1H chemical shifts (δH) of poly (methyl methacrylate) (PMMA), poly (4-vinyl phenol) (PVPh) and their polymer blends. Density functional theory (DFT) was used to computeδH of hydroxyl groups (OH) for both PVPh homopolymer and PMMA/PVPh polymer blends. The calculated values for δH of OH groups with or without forming hydrogen bonds agreed reasonably well with the experimental values. It was found that the δH of OH groups moved downfield when they formed hydrogen bonds with both other OH groups and carbonyl groups (C=O). The simulated solid state 1H 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 1H NMR spectra are influenced by the main-chain conformations and the hydrogen bond types.