DETERMINATION OF ORIENTATIONAL ANISOTROPY IN GLASSY SOLIDS BY 2D DIPOLAR SPECTRA WITH SAMPLE FLIPPING

A method is proposed for the quantitative measurement of orientational anisotropy in glassy solids based on 2D dipolar NMR spectra with samp le flipping (dipolar DECODER experiment). Purely dipolar spectra are o btained by chemical shift refocusing by a multiple pulse sequence. The experiment is applied to an investigation of a doubly C-13-labeled sa mple of bisphenol-A polycarbonate deformed in a channel-die apparatus. The orientational distribution function is determined by an expansion of the distribution in terms of spherical harmonics up to degree four . (C) 1997 Academic Press.