| Abstract: | Two-dimensional (2D) NMR is a versatile technique which exists in many versions. Two broad classes of 2D techniques are (1) correlated spectroscopy and (2) J-resolved spectroscopy. The first of these may be divided into two further subdivisions: COSY, which permits correlations of resonances via J-coupling, and NOESY, which allows direct measurement of intenuclear (usually interproton) distances by the nuclear Overhauser effect. COSY greatly facilitates the interpretation of complex spectra and spectral interpretation in terms of stereochemical sequences is placed on a firmer foundation. NOESY provides direct information concerning the local conformations of polymers in solution. By use of J-resolved 2D NMR, we can separate J-couplings and chemical shifts on different axes and thus achieve a degree of resolution of both these parameters far beyond what is attainable in the 1D spectrum. Finally, we may combine correlated and J-resolved spectroscopy and achieve the benefits of both in 3D NMR, in which the 2D cross peaks exhibit J-coupling fine structure. These techniques are illustrated for a variety of polymers including poly(methyl methacrylate), poly(vinyl fluoride), poly-y-benzyl L-glutamate, and poly(propylene oxide). |
