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A new polymerization method, termed as step transfer-addition and radical-termination, is developed for the step-growth radical polymerization of α,ω-unconjugated dienes under irradiation of visible light at room temperature (25 °C) for the first time. α,ω-Diiodoperfluoroalkane monomers (signified as A) are added onto α,ω-unconjugated dienes (signified as B) alternatively and efficiently with the generation of perfluorocarbon-containing alternating copolymers ( AB) n. Based on the combined analyses of polymerization kinetics and NMR spectra (1H and 19F), the mechanism of the novel polymerization method, including the side reaction, is proposed. This novel polymerization method provides a new strategy not only for the step-growth radical polymerization of α,ω-unconjugated dienes but also for the construction of high molecular weight perfluorocarbon-containing alternating copolymers. [ABSTRACT FROM AUTHOR]

A new pulse sequence for obtaining 19F detected DOSY (diffusion ordered spectroscopy) spectra of fluorinated molecules is presented and used to study fluoropolymers based on vinylidene fluoride and chlorotrifluoroethylene. The performance of 19F DOSY NMRexperiments (and in general any type of NMR experiment) on fluoropolymers creates someunique complications that very often prevent detection of important signals. Factors that create these complications include: (1) the presence of many scalar couplings among 1H, 19F and13C; (2) the largemagnitudes of many 19F homonuclear couplings (especially 2JFF); (3) the large 19F chemical shift range; and (4) the low solubility of these materials (which requires that experiments be performed at high temperatures). A systematic study of the various methods for collecting DOSY NMR data, and the adaptation of these methods to obtain 19F detected DOSY data, has been performed using a mixture of low molecular weight, fluorinated model compounds. The best pulse sequences and optimal experimental conditions have been determined for obtaining 19F DOSY spectra. The optimum pulse sequences for acquiring 19F DOSY NMR data have been determined for various circumstances taking into account the spectral dispersion, number and magnitude of couplings present, and experimental temperature. Pulse sequences and experimental parameters for optimizing these experiments for the study of fluoropolymers have been studied. [ABSTRACT FROM AUTHOR]

A new pulse sequence for obtaining 19 F detected DOSY (diffusion ordered spectroscopy) spectra of fluorinated molecules is presented and used to study fluoropolymers based on vinylidene fluoride and chlorotrifluoroethylene. The performance of 19 F DOSY NMR experiments (and in general any type of NMR experiment) on fluoropolymers creates some unique complications that very often prevent detection of important signals. Factors that create these complications include: (1) the presence of many scalar couplings among 1 H, 19 F and 13 C; (2) the large magnitudes of many 19 F homonuclear couplings (especially 2 J FF ); (3) the large 19 F chemical shift range; and (4) the low solubility of these materials (which requires that experiments be performed at high temperatures). A systematic study of the various methods for collecting DOSY NMR data, and the adaptation of these methods to obtain 19 F detected DOSY data, has been performed using a mixture of low molecular weight, fluorinated model compounds. The best pulse sequences and optimal experimental conditions have been determined for obtaining 19 F DOSY spectra. The optimum pulse sequences for acquiring 19 F DOSY NMR data have been determined for various circumstances taking into account the spectral dispersion, number and magnitude of couplings present, and experimental temperature. Pulse sequences and experimental parameters for optimizing these experiments for the study of fluoropolymers have been studied. Copyright © 2016 John Wiley & Sons, Ltd., (Copyright © 2016 John Wiley & Sons, Ltd.)