| 초록 |
Ferroelectric polymeric materials such as poly vinylidene fluoride (PVDF) are particularly of interest for non-volatile flexible memory application due to their bistability and large permanent polarization. PVDF exhibits at least three crystalline forms including α, β, and γ, among which the β phase is the most important because of its intrinsic ferroelectric properties. Therefore, it is critical to manipulate the types of PVDF crystal phase and orientation to fully utilize the material properties. We investigated the control of pressure driven polymorphic transition of PVDF by using micro/nanoimprint lithography. It is well-known that melt crystallization of the PVDF at atmospheric pressure yields the α type crystal. We observed that the pressure applied on the selective areas of polydimethylsiloxane (PDMS) mold transferred α type crystal structure into γ one in certain temperature range, giving rise to micro/nano patterned topographic as well as polymorphic α and γ structure. Several PDMS patterns such as hexagonal, line, square and reverse hexagonal were used. The patterned structures were characterized by Fourier Transform Infrared Spectroscopy (FTIR), X-Ray Diffractometer (XRD), Scanning and Transmission electron microscope (SEM and TEM). |
