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 sample flipping (dipolar DECODER experiment). Purely dipolar spectra are obtained by chemical shift refocusing by a multiple pulse sequence. The experiment is applied to an investigation of a doubly 13C-labeled sample 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.