Studies on Control of Higher Oder Structures of Ferrelectric Polymer Crystals and Their Applications

本研究旨在进一步了解铁电聚合物的介电、机械和机电性能，通过控制铁电聚合物晶体的微观结构来开发在高温下稳定的高灵敏度压电聚合物，以及为新开发的压电聚合物材料的应用提供基础。研究的材料主要是偏氟乙烯/三氟乙烯共聚物[P（VDF/TrFE）]和聚偏氟乙烯（PVDF）。主要研究结果如下：1. P（VDF/TrFE）单晶薄膜是由单轴拉伸薄膜在六方相（顺电相）晶化形成的，它包含在三个主轴上具有高度择优取向的完全伸展的链晶体.通过在六方相P（VDF/TrFE）中结晶，成功地获得了由完全伸展链晶体组成的P（VDF/TrFE）/PMMA共混膜。高度结晶，单晶 ...更多信息 还发现聚乙烯的类塔尔膜是通过单轴拉伸膜在高压下结晶形成的，其中六方相是结晶稳定状态。所得膜是光学透明的并且不包括层状晶体。研究了P（VDF/TrFE）单晶薄膜在较宽温度范围内的弹性、介电和压电性能。这些测量和X射线衍射研究揭示了晶格中链状分子在铁电（R）_c相和顺电相运动的精确信息。发现顺电相为液晶态. PVDF和具有高摩尔含量的VDF的P（VDF/TrFE）在六方相下的高压结晶产生β形式的延伸链晶体，其表现出强的压电效应，该压电效应在高达熔点（PVDF为205 ° C）下稳定。利用P（VDF/TrFE）的厚度剪切压电振动模式，研制了一种新型的横向超声换能器。这些传感器的灵敏度被发现非常高的陶瓷传感器相比。少

This research project was performed for further understanding on dielectric, mechanical, and electromechanical properties of ferroelectric polymers, for development of piezoelectric polymers with high sensuitivity stable at high temperatures by controling micro-structures of ferroelectric polymer crystals, and for applications of newly developed piezoelectric polymer materials. The meterials mainly studied were vinylidene fluoride trifluoroethylene copolymers [P(VDF/TrFE)] and poly (vinylidene fluoride) (PVDF). The followings are the main results :1. P (VDF/TrFE) single crystaline films comprising fully extended chain crystals having highly preferential orientattion in three principal axs were found to be formed by crystallizing a uniaxilly stretched film in the hexagonal (paraelectric) phase.2. P (VDF/TrFE)/PMMA blend films composed of fully extended chain crystals were sucessfully obtained by the crystallization in the hexagonal phase of P (VDF/TrFE). Highly crystallized, single-crys … More tal-like films of polyethylene were also found to be formed by crystallization of uniaxially strethe film under high pressure where the hexagonal phase is thermodynamically stable state. The resulting film is optically transparent and includes no lamellar crystal.3. The elastic, dielectric, and piezoelectric properties of the single crystalline film of P (VDF/TrFE) were studied in a wide temperature range. The film has the highest piezoelectric activities ever found. These measurements and X-ray diffraction study revealed orecise information about the motions of chain molecules in crystal lattices both in ferroelect (R)^<^>c phase and paraelectric phaswe. The paraelectric phase is found to be a liquid crystalline state.4. High-pressure crystallization of PVDF and P (VDF/TrFE) with high molar content of VDF under the hexagonal phase yielded beta-form extended chain crystals which exhibit strong piezoelectric effects stable up to the melting points (205ﾟC for PVDF).5. Novel ultrasonic transducers for transverse ultrasonic waves were developed using thiekness shear piezoelectric vibration mode of P (VDF/TrFE). The sensitivity of these transducers were found very high comparable to that of ceramic transducers. Less