Studies on the Molecular Chain Motions, the Ordered Structure Formation Process, and Development Mechanisms of Functionality Properties in Single Crystalline Films of Ferroelectic Polymers

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The single crystalline film (SCF) of ferroelectric copolymer of vinylidene fluoride and trifluoroethylene, P (VDF/TrFE), is a highly crystallized, highly double-oriented, lamellar-crystal-free film. Since the SCF often exhibits theproperties very close to those of a single crystal, it is the best material for investigation of various problems in ferroelecric polymers such as formation mechaisms of ordered structure in SCF, paraelectric-ferroelectric phase transition, chain motions in the cystal, etc. In this research project, we investigate higher-order structure of SCF and its anisotropic properties relevalent to these problems by using various techniques such as X-ray diffraction, POM, SEM, TEM, DSC, piezoelectic resonance, dielectric relaxaton measurements, Brillouin scattering, NMR, etc. The main results obained are as follows. (1) The preferenial orienation of the c-axis (chain axis) and b-axis (polar axis) in the SCF develops in the paraelectric phase. In the SCF, the orthorhombi … More c (110) crystal plane is strictly parallel to the film surface, indicating that the crystal surface free energy is ant essential factor to determine the preferential orientation of hexagonal (100) plane. Annealing in the paraelectric phase for long period (e.g. 100h) eliminates crystal defects, which makes the stiffness of SCF very high : we suceesfully obtained the SCF having Youngs's modulus as high as 204 GPa at 10K.(2) The molecular chain motion in the paraelectric phase is definitely clarified by X-ray diffraction, dielectric relaxation measurements, NMR spin lattice relaxation, and shear mechanical properties : each chain molecule of TGTG' conformation undergoes the flip-flop motion and rotational motion independently of neighboring chain molecules in the hexagonal crystal, a crystal having liquid crystal characteristic. Based on these information we establish to a new concept to explain the anomalous dielectric properties appearing in the paraelectric phase. Useful information on the phase transition has been also obtained by Brillouin scattering. (3) The SC film has effective shear piezoelectricity. We developed transducers for transverse ultrasonic waves. They are useful for non-destractive inspection of industrial materials. (4) The SCF has large Pockels effect, and is potentially useful as electrooptical devices. (5) We have obtained some useful and interesting results on the structure and properties of oriented films of P(VDF/TrFE)/at-PMMA blends. Less