W. Chassé, J. L. Valentín, G. D. Genesky, C. Cohen, K. Saalwächter.
Precise dipolar coupling constant distribution analysis in proton multiple-quantum NMR of elastomers.
J. Chem. Phys. 134, 044907 (2011). DOI 10.1063/1.3534856.
Abstract
In this work we present an improved approach for the analysis of ¹H double-quantum nuclear magnetic resonance build-up data, mainly for the determination of residual dipolar coupling constants and distributions thereof in polymer gels and elastomers, yielding information on crosslink density and potential spatial inhomogeneities. We introduce a new generic build-up function, for use as component fitting function in linear superpositions, or as kernel function in fast Tikhonov regularization (ftikreg). As opposed to the previously used inverted Gaussian build-up function based on a second-moment approximation, this method yields faithful coupling constant distributions, as limitations on the fitting limit are now lifted. A robust method for the proper estimation of the error parameter used for the regularization is established, and the approach is demonstrated for different inhomogeneous elastomers with coupling constant distributions.