Studies on switching mechanism of ferroelectric polymer liquid crystals by time-resolved optical waveguide spectroscopy

1.时间分辨光波导光谱（TROWS）的发展大多数铁电液晶的开关时间从微秒到毫秒不等，这意味着必须开发时间分辨率快于微秒的仪器。本研究的第一步就是围绕这一问题展开的，我们研制的TROWS可以检测到每几十纳秒一次开关下的瞬态光波导模式。2.流动分子量液晶的动力学首次将TROWS技术应用于低分子量液晶的研究。用多层近似法分析了外电场作用下分子的运动，得到了垂直取向和平行取向两种稳定态之间的角度分布及其时间依赖关系. 3.铁电液晶瞬态结构的研究 ...更多信息 通过对波导模式的分析，我们发现了近晶层（如书架、人字形、书架）的瞬态弯曲运动，揭示了在开关过程中，在电极之间的上半部分和下半部分中的分子发生不连续，4.铁电聚合物液晶的开关机理研究了铁电聚合物液晶的开关机理，研究的基础上获得的知识低分子量的。瞬态波导图案清楚地表明近晶层以及低分子量液晶的弯曲运动的存在。由于聚合物主链位于近晶层之间，它们对介晶侧链的旋转运动几乎没有影响，介晶侧链在交变电场下在层间进行共格运动。这些协同运动使得侧链能够以与低分子液晶一样快的速度切换它们的取向。少

1.Development of time-resolved optical waveguide spectroscopy (TROWS)The switching times of most ferroelectric liquid crystals range from micro-to milli-second, which means one must develop an instrument with a time-resolution faster than microsecond. The first step of this research was conserned with this issue, and the TROWS we made could detect transient optical waveguide mode patterns under the switching every a few tens nanoseconds.2.Dynamics of flow molecular weight nematic liquid crystalsThe new technique using TROWS was applied firstly to the study of low molecular weight nematic liquid crystals. The molecular motion under external electric field was analyzed by a multi-layr approximation, showing that the angle distribution and its time dependence between two stable states of homeotropic and parallel orientations.3.Studies on transient structures of a ferroelectric liquid crystalThe internal structures of a ferroeletric liquid crystal under a static high-electric feild and und … More er the inversion of its polarity, were investigated.From the analysis of waveguide modes, we found a transient bending motion of the smectic layrs such as bookshelf*chevron*bookshelf, and it was revealed that on the way of switching, the molecules in upper and lower halves between the electrodes take place an unti-symmetrical cone motion synchronized with the bending of chevron structure.4.Switching mechanism of ferroelectric polymer liquid crystalsFerroelectric polymer liquid crtstals were investigated on the basis of the knowledge obtained for low molecular weight ones. The transient waveguide patterns clearly showed the existence of bending motion of smectic layrs as well as low molecular weight liquid crystals. Since the polymer main chains locate between smectic layrs, they have little effect on the rotational motion of the mesogenic side chains, which perform a coherent motion among layrs under alternating electric field. These cooperative motions enable the side chains to switch their orientation with a high speed as fast as low molecular liquid crystals. Less