Lattice-Stiffening Transition in Copolymer Films of Vinylidene Fluoride (70%) with Trifluoroethylene (30%)

Authors

C.N. Borca, University of Nebraska-Lincoln
Shireen Adenwalla, University of Nebraska-LincolnFollow
Jaewu Choi, University of Nebraska-LincolnFollow
P.T. Sprungerr, Louisiana State University
Stephen Ducharme, University of NebraskaFollow
Lee Robertson, High Flux Isotope Reactor (HFIR), Oak Ridge National Laboratory, Oak Ridge, Tennessee
S.P. Palto, University of Nebraska-Lincoln
Jianglai Liu, University of Nebraska-Lincoln
Matt Poulsen, University of Nebraska-LincolnFollow
V.M. Fridkin, Institute of Crystallography, The Russian Academy of Sciences, Moscow, Russia
H. You, Material Science Division 223, Argonne National Laboratory, Argonne, Illinois
Peter A. Dowben, University of Nebraska-LincolnFollow

Date of this Version

11-29-1999

Comments

Published American Physical Society. Copyright 1999. Permission to use. Phys. Rev. Lett. 83 (1999) 4562-4565. http://prb.aps.org/.

Abstract

We report the discovery of a compressibility phase transition at 160 K in crystalline copolymer films of vinylidene fluoride ( 70%) with trifluoroethylene ( 30%). This phase transition is distinct from the known bulk ferroelectric-paraelectric phase transition at 353 K and surface ferroelectric phase transition at 295 K. The new phase transition is characterized by an increase in the effective Debye temperature from 48 to 245 K along the 〈010〉 direction as the temperature falls below 160 K. This phase transition is evident in neutron scattering, x-ray diffraction, angle-resolved photoemission, and in the dipole active phonon modes in electron energy-loss spectroscopy.