Selective measurement of heteronuclear 1H-13C dipolar couplings in motionally heterogeneous semicrystalline polymer systems

J Phys Chem A. 2005 Jun 16;109(23):5050-4. doi: 10.1021/jp0503821.

Abstract

A pulse sequence for the selective recoupling of heteronuclear dipolar interactions in mobile amorphous phase of powdered semicrystalline polymers is described. 1H-13C dipolar interactions are selectively measured by PISEMA-type sequence. Selection of 13C magnetization originating from amorphous phase is achieved by a train of saturation pulses followed by a short delay and a direct excitation pulse on 13C spins. The development of undesired net 13C magnetization during the recoupling sequence is prevented by the efficient "reverse" 13C --> 1H cross-polarization. The efficacy of the 2D method to measure 1H-13C dipolar couplings selectively for mobile components is demonstrated on powdered crystalline L-alanine, semicrystalline polyethylene, and nanocomposite polyamide-6/montmorillonite.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alanine / chemistry
  • Bentonite / chemistry
  • Caprolactam / analogs & derivatives
  • Caprolactam / chemistry
  • Carbon Isotopes / chemistry*
  • Hydrogen / chemistry*
  • Magnetic Resonance Spectroscopy
  • Nanocomposites
  • Polyethylenes / chemistry
  • Polymers / chemistry*

Substances

  • Carbon Isotopes
  • Polyethylenes
  • Polymers
  • Bentonite
  • nylon 6
  • Caprolactam
  • Hydrogen
  • Alanine