Carbon‐13 NMR relaxation and transitions in polymers

Abstract

High‐resolution proton‐decoupled carbon‐13 nuclear magnetic resonance relaxation parameters have been obtained as a function of temperature for a set of completely amorphous polymers, semicrystalline polymers, and a series of ethylene–vinyl acetate copolymers. With these samples the nature of the glass temperature, other postulated amorphous transitions, and the β transition were investigated. For the completely amorphous polymers, the average correlation times depend on temperature according to the Williams–Landel–Ferry relation. Spectral collapse occurs at temperatures whose ratio to Tg is in the range 1.2–1.4 and corresponds to a correlation time of about 10−7s. The loss of resolvable spectra is demonstrated to be a consequence of experimental methods and is not due to the occurrence of another amorphous transition. Both the methylene and methine carbons can be resolved for the ethylenevinyl acetate copolymers. Although the correlation time for the methylene carbon is continuous and resolvable through the β transition region, the methine branch‐point resonance is lost. The implication of these results to the molecular nature of the β transition is discussed.

Polymer conformational structure and dynamics at the glass transition studied by multidimensional 13C NMR

“…When all of these data are combined with those determined earlier through I3C spin-lattice relaxation times by Mandelkern et al [43] at elevated temperatures, the mean correlation times can be followed over more than 12 orders of magnitude. As demonstrated in Fig.…”

Predicting polymer/solvent diffusion coefficients using free‐volume theory

“…An Recent NMR studies have shown that variable temperature I3C spin-lattice relaxation studies can be used successfully in calculating both polymer and solvent WLF coefficients (Schaefer et al, 1990; Dekmezian et al, 1985;Zielinski et al, 1992a), thereby offering a viable option to viscosity measurements.…”

Does Positronium Feel Dynamics of Polymer Chain?

“…NMR or viscosity measurements [14][15][16] are given for comparison. The temperature T f , in which the fast process observed by quasielastic neutron scattering starts to appear, is also displayed.…”