高分子混摻共價鍵與氫鍵彎曲型液晶分子之影響

Abstract

本實驗可分成兩大系列，其一，取氫鍵高分子，與五環的香蕉 型共價鍵小分子做混摻；其二，取五環的香蕉型共價鍵高分子，與氫 鍵小分子做混摻，並做偏光顯微鏡(POM)，示差掃描熱量計(DSC)， X-ray 粉末射線繞射儀 (PXRD)，以及三角波法做光電量測並探討其 性質。比較之下共價鍵液晶小分子混入氫鍵高分子效果較佳，所有的 混合物都具有Sm CP phase，而氫鍵小分子混入共價鍵高分子需要超 過50wt%小分子才有液晶相。 另外，混入液晶相較廣之共價鍵分子可以大幅增廣該系列混摻物 之液晶相範圍，而且較少的共價鍵則可降低PS 值的飽和電壓。 再者，混摻物d-spacing，domain 大小，PS 值都與混摻比例有關， 尤其是PS 值在系列一，也就是氫鍵高分子混摻共價鍵小分子時，單 氫鍵與共價鍵混摻系列上幾乎呈線性關係，故可以經由調整混摻比例 達到所希望的PS 值。

In order to improve the properties of H-bonded bent core mesogens, there is two series for our research, one is mixtures of single hydrogen bonded banana-shaped polymer doped with covalent bonded banana-shaped liquid crystals；another is mixtures of single hydrogen bonded banana-shaped compound doped with covalent bonded banana-shaped polymer. The phases were demonstrated by polarized light optical microscopy (POM), differential scanning calorimetry (DSC), powder X-ray diffraction (XRD), and electro-optical properties based on dielectric response as well as measurements of polarization reversal current. The temperature range of the B2 phase of mixtures was extended from several degrees to about fifteen to thirty degrees due to the contribution of covalent bonded LCs；for both series, as polymer is less than 20 wt％, the spontaneous polarization (PS) shows up；moreover, the spontaneous polarization (PS) of single H-bonded LCs was increased from about 250 nC/cm2 to 500 nC/cm2 with the increasing of the percentage of the covalent bonded mesogens linearly. The relationships between Ps value and applied voltage were also studied. Saturated applied voltage can be reduced by doping H-bonded mesogens in covalent bonded LCs.