W. Chassé, J. L. Valentín, G. D. Genesky, C. Cohen, K.
Precise dipolar coupling constant distribution analysis in
proton multiple-quantum NMR of elastomers.
J. Chem. Phys. 134,
044907 (2011). DOI 10.1063/1.3534856.
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.