DETERMINATION OF MONOMER CONFORMATIONS IN NONCRYSTALLINE SOLID POLYMERS BY 2-DIMENSIONAL NMR EXCHANGE SPECTROSCOPY

We propose and demonstrate a new approach to the determination of the conformations of molecules or monomers in noncrystalline solids. The m ethod makes use of two-dimensional NMR exchange spectroscopy in combin ation with specific isotopic labeling. We present experimental results on specifically labeled poly(methyl methacrylate), poly(methyl acryla te), and poly(ethyl methacrylate). Through comparisons between the exp erimental and simulated two-dimensional spectra, we determine that the ester side groups of poly(methyl methacrylate) and poly(methyl acryla te) have planar, trans conformations and that the side groups of poly( ethylmethacrylate) are also predominantly in the planar, trans conform ation in the noncrystalline solid state. We discuss potential applicat ions of this approach in structural studies of synthetic polymers, bio logical systems, and other disordered solids.