title: Selective measurement of heteronuclear 1H-13C dipolar couplings in motionally heterogeneous semicrystalline polymer systems.
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.
authors.affiliation: Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Heyrovsky sq. 2, 162 06 Prague 6, Czech Republic. brus@imc.cas.cz
authors.forename: Jiri
authors.initials: J
authors.lastname: Brus
authors.forename: Martina
authors.initials: M
authors.lastname: Urbanova
mesh_terms: D000409:Alanine / Q000737:chemistry; D001546:Bentonite / Q000737:chemistry; D002209:Caprolactam / Q000031:analogs & derivatives / Q000737:chemistry; D002247:Carbon Isotopes / Q000737:chemistry*; D006859:Hydrogen / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D053761:Nanocomposites; D011095:Polyethylenes / Q000737:chemistry; D011108:Polymers / Q000737:chemistry*
chemical_list: D002247:Carbon Isotopes; D011095:Polyethylenes; D011108:Polymers; D001546:Bentonite; C009916:nylon 6; D002209:Caprolactam; D006859:Hydrogen; D000409:Alanine