Multinuclear Magnetic Resonance and DFT Studies of the Poly(chlorotrifluoroethylene-alt-ethyl vinyl ether) Copolymers

Chlorotrifluoroethylene (CTFE) and ethyl vinyl ether (EVE) were reacted under radical conditions to produce the poly(CTFE-co-EVE) alternating copolymer, and a full C-13, H-1, and F-19 NMR structural interpretation is offered. All spectra were characterized by broad signals resulting from the overlapping of different chemical shifts. This observation was rationalized by considering a complex mixture of diastereomerically related Compounds, hence allowing an average assignment to be determined. A density functional theory (DFT) Computational study of the isotropic magnetic shieldings with the GIAO and CSGT methods was performed to explore the diasteriomeric relationships between the single building blocks and their mutual influences along the polymer chain. The calculated results totally support the assignment of the experimental chemical shifts of two diasteriomeric sets of resonances indicating chiral center inversion, and not spin-spin J coupling interactions, as the main cause of spectral complexity.