SSNMR; 19F NMR of polymers; Hazendonk

Solid State Nuclear Magnetic Resonance
Vol: 30, Issue: 2, September, 2006 Bibliographic Page
pp. 114-123

Title: Fluorine-19 solid state NMR study of vinylidenefluoride polymers using selective relaxation filters
Authors: Wormald, Philipa; Ameduri, Brunob; Harris, Robin K.c; Hazendonk, Pauld
Affiliations: a. School of Chemistry, University of St Andrews, Purdie Building, St. Andrews KY16 9ST, UK
b. Laboratory of Macromolecular Chemistry, Ecole Nationale de Chimie de Montpellier, Unite Mixte Recherche CNRS 5076, 8 rue de l’Ecole Normale, F 34296 Montpellier, Cedex 5, France
c. Department of Chemistry, University of Durham Science Laboratories, South Road, Durham DH1 3LE, UK
d. Department of Chemistry and Biochemistry, 4401 University Drive, University of Lethbridge, Alberta, Canada
Keywords: 19F solid-state NMR; Relaxation filters; Fluoropolymers; High-speed MAS; Vinylidene fluoride; Telomer
Abstract (English):

Two fluoropolymers, poly(vinylidenefluoride) (PVDF) and a vinylidenefluoride telomer (VDFT), with molecular weights of 1×106 and 2×103Da by GPC, respectively, have been analysed by 19F solid-state nuclear magnetic resonance (NMR) spectroscopy. Relaxation-filtered proton-decoupled magic-angle spinning (MAS) experiments, namely T1r filter, dipolar filter (DF), direct-polarisation delayed acquisition (DPDA) and discrimination induced by variable-amplitude minipulses (DIVAM), allowed signals in the direct polarisation (DP) spectra of PVDF and the VDFT to be discussed in terms of rigid and mobile domains. Both samples showed signals, which were multi-componential, but they differ in the nature of the crystalline form present. Thus, the Vinylidenefluoride (VDF) telomer exhibited a crystalline component corresponding to b PVDF, whereas the PVDF contained crystallites of the a form. Signals relating to end groups and reverse units, plus an anomalous signal displaying long-time transverse relaxation in the DPDA spectrum, were found for both polymers, though they showed diversity in chemical shift and content. Signals related to reverse units and/or end groups were seen between approximately -115 and approximately -117ppm for both samples. High-speed MAS at higher magnetic field resulted in an increase in resolution so that signals previously attributed to single-phase characteristics are shown to indicate the possibility of several different mobilities. The results are debated with respect to molecular weight and relaxation parameters.