Solid-state NMR as a powerful tool for the structural and dynamic characterization of insoluble perfluoropolyether-tetrafluoroethylene block copolymers

This work reports on a solid-state NMR (SSNMR) methodological approach for the characterization of perfluoropolyether-tetrafluoroethylene block copolymers (PFPE-b-TFE). While solution state NMR was successfully used for the study of PFPE-b-TFE copolymers with short PTFE blocks that are liquid or wax-like at room temperature, it could not be applied to copolymers with longer PTFE blocks that are solid and insoluble in fluorinated solvents. In this work a combination of 13C high- and 19F high- and low-resolution SSNMR experiments was used to obtain information on the structural and dynamic properties of PFPE-b-TFE copolymers with PTFE blocks longer than 10 carbon atoms, wax-like or solid at room temperature. 19F SSNMR spectra allowed important structural properties such as TFE molar fraction and block length to be determined. On the other hand, 13C selective experiments and 19F FID analysis gave insights into the dynamic properties of the PFPE and PTFE blocks, which were compared with those of the neat components. Indications of the presence of an interface with intermediate properties were obtained.