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 method makes use of two-dimensional NMR exchange spectroscopy in combination with specific isotopic labeling. We present experimental results on specifically labeled poly(methyl methacrylate), poly(methyl acrylate), and poly(ethyl methacrylate). Through comparisons between the experimental and simulated two-dimensional spectra, we determine that the ester side groups of poly(methyl methacrylate) and poly(methyl acrylate) have planar, trans conformations and that the side groups of poly(ethylmethacrylate) are also predominantly in the planar, trans conformation in the noncrystalline solid state. We discuss potential applications of this approach in structural studies of synthetic polymers, biological systems, and other disordered solids.