Determination of Molecular Orientational Order in Cold-Stretched Poly( p-phenylene vinylene) Thin Films by DECODER 13C NMR

• Published in: Solid state nuclear magnetic resonance 2002-09, Vol.22 (2), p.275-297
• Main Authors: Kropewnicki, Michelle L., Schaefer, Dieter J., Hehn, Manfred, Dermaut, Wim, Geise, Herman J., Chmelka, Bradley F.
• Format: Article
• Language: English
• Subjects: Anisotropy; Carbon Radioisotopes; Computer Simulation; Crystallography - methods; Magnetic Resonance Spectroscopy - instrumentation; Magnetic Resonance Spectroscopy - methods; Membranes, Artificial; Models, Chemical; Models, Molecular; Molecular Conformation; Polyvinyls - chemistry; Protons
• ISSN: 0926-2040; 1527-3326
• DOI: 10.1006/snmr.2002.0082

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 λ=l/l 0=5. The unstretched films were found to be moderately ordered, comprised of a component present at 80% with a Gaussian distribution of 60° fwhm, while the remaining 20% is isotropically distributed. A distribution of 9°±3° 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.