title: Determination of molecular orientational order in cold-stretched poly(p-phenylene vinylene) thin films by DECODER 13C NMR.
abstract: The properties of poly(p-phenylene vinylene) (PPV) films depend on the degree of orientational order present in the films. Recently, Dermaut et al. reported a novel cold-stretching technique (Macromolecules 33, 5634-5637 (2000)) in which chain alignment can be introduced into PPV precursor films by uniaxially stretching them prior to the thermal elimination reaction that forms PPV. The two-dimensional direction exchange with correlation for orientation-distribution evaluation and reconstruction (DECODER) 13C NMR technique was applied to both unstretched PPV films and PPV films that were uniaxially cold stretched to a draw ratio lambda = l/l0 = 5. The unstretched films were found to be moderately ordered, comprised of a component present at 80% with a Gaussian distribution of 60 degrees fwhm, while the remaining 20% is isotropically distributed. A distribution of 9 degrees +/- 3 degrees fwhm was measured by NMR in good agreement with IR dichroism measurements for the uniaxially cold-stretched films, establishing that a high degree of orientational order can be introduced by cold stretching PPV films.
authors.affiliation: Department of Chemical Engineering, University of California, Santa Barbara, California 93106, USA.
authors.forename: Michelle L
authors.initials: ML
authors.lastname: Kropewnicki
authors.forename: Dieter J
authors.initials: DJ
authors.lastname: Schaefer
authors.forename: Manfred
authors.initials: M
authors.lastname: Hehn
authors.forename: Wim
authors.initials: W
authors.lastname: Dermaut
authors.forename: Herman J
authors.initials: HJ
authors.lastname: Geise
authors.forename: Bradley F
authors.initials: BF
authors.lastname: Chmelka
mesh_terms: D016880:Anisotropy; D002250:Carbon Radioisotopes; D003198:Computer Simulation; D003461:Crystallography / Q000379:methods*; D009682:Magnetic Resonance Spectroscopy / Q000295:instrumentation* / Q000379:methods*; D008567:Membranes, Artificial; D008956:Models, Chemical; D008958:Models, Molecular; D008968:Molecular Conformation; D011145:Polyvinyls / Q000737:chemistry*; D011522:Protons
chemical_list: D002250:Carbon Radioisotopes; D008567:Membranes, Artificial; D011145:Polyvinyls; D011522:Protons; C470024:poly(4-phenylenevinylene)