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Title: Effects of configurational changes on molecular dynamics in polyvinylidene fluoride and poly(vinylidene fluoride-trifluoroethylene) ferroelectric polymers

We present a comparative study of proton dynamics in unpoled non-ferroelectric polymer polyvinylidene fluoride (PVDF) and in its trifluoroethylene containing ferroelectric copolymer (with 70/30 molar proportion), using quasi-elastic neutron scattering. The neutron data reveal the existence of two distinct types of molecular motions in the temperature range investigated. The slower motion, which is characterized in details here, is ascribed to protons jump diffusion along the polymeric carbon chains, while the faster motion could be attributed to localized rotational motion of methylene groups. At temperatures below the Curie point (T{sub c} ∼ 385 K) of the composite polymer, the slower diffusive mode experiences longer relaxation times in the ferroelectric blend than in the bare PVDF, although the net corresponding diffusion coefficient remains comparatively the same in both polymers with characteristic activation energy of E{sub A} ≈ 27–33 kJ/mol. This arises because of a temperature dependent jump length r{sub 0}, which we observe to be effectively longer in the copolymer, possibly due to the formation of ordered ferroelectric domains below T{sub c}. Above T{sub c}, there is no appreciable difference in r{sub 0} between the two systems. This observation directly relates the known dependence of T{sub c} on molar ratio to changes in r{sub 0}, providing fundamental insightmore » into the ferroelectric properties of PVDF-based copolymers.« less
Authors:
 [1] ;  [2] ;  [3] ;  [4] ;  [5]
  1. Jülich Centre for Neutron Science, Forschungszentrum Jülich GmbH, 52428 Jülich (Germany)
  2. (United States)
  3. Department of Physics and Materials Science, City University of Hong Kong, Kowloon (Hong Kong)
  4. Biology and Soft-Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States)
  5. Chemical and Engineering Materials Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States)
Publication Date:
OSTI Identifier:
22489169
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 107; Journal Issue: 8; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; ACTIVATION ENERGY; CARBON; COPOLYMERS; CURIE POINT; DIFFUSION; FERROELECTRIC MATERIALS; FLUORINATED ALIPHATIC HYDROCARBONS; MOLECULAR DYNAMICS METHOD; NEUTRON DIFFRACTION; POLYVINYLS; PROTONS; TEMPERATURE DEPENDENCE; TEMPERATURE RANGE