SOLID-STATE C-13 NMR-STUDIES OF MODEL URETHANE ELASTOMERS

Model urethane elastomers consisting of 4,4ʹ-methylene diisocyanate, 1,4-butanediol, and a 2000 molecular weight poly(oxypropylenediol) were examined by solid-state carbon-13 NMR spectroscopy. T1ρc values were determined for the aromatic and butanediol carbons as a function of cross polarization field strength and temperature. The results for the aromatic carbons correlate well with observed high-temperature behavior of the elastomer as determined by dynamic mechanical spectroscopy. The biexponential decay of the butanediol resonances indicated that two types of motional populations can be associated with the phase-segregated portion of the hard segment. These results demonstrate the intimate connection between molecular motion and mechanical properties in urethane polymers. This understanding provides an important framework for optimizing physical properties in urethane polymers. © 1990, American Chemical Society. All rights reserved.