CONFORMATIONAL EFFECTS AND CONFIGURATIONAL SPLITTING IN C-13 NMR-SPECTRA OF SYNTHETIC-POLYMERS AS INVESTIGATED BY AB-INITIO INDIVIDUAL GAUGES FOR LOCALIZED MOLECULAR-ORBITALS (IGLO) CALCULATIONS

The inhomogeneous broadening of solid state C-13 spectra of glassy polymers and the configurational splitting observed in solution spectra are analyzed by a unifying approach. The method combines conformational statistics and ab initio IGLO calculations to obtain simulated solid state and solution spectra. A number of polymers of different structural classes are investigated, including poly(ethylene), atactic poly(propylene), poly(vinyl chloride), and poly(methyl methacrylate). For most systems a remarkable degree of agreement between simulation and experiment is achieved for both the solid state NMR and the configurational splitting. Furthermore, the influence of geometric parameters on the chemical shift, the validity of the gamma-gauche effect, an MO analysis, and the role of the anisotropic part of the chemical shift tensor as a source of structural information are considered.