| 研究生: |
楊書寧 Yang, Shu-Ning |
|---|---|
| 論文名稱: |
中孔洞氧化矽空心球在液晶之散射機制與溫度之關係 The correlation between the scattering mechanism of mesoporous silica hollow sphere in LCs and temperature |
| 指導教授: |
羅光耀
Lo, Kuang-Yao |
| 學位類別: |
碩士 Master |
| 系所名稱: |
理學院 - 物理學系 Department of Physics |
| 論文出版年: | 2016 |
| 畢業學年度: | 104 |
| 語文別: | 英文 |
| 論文頁數: | 73 |
| 中文關鍵詞: | 液晶 、穿透光譜 、介電係數 |
| 外文關鍵詞: | Liquid crystals, Light scattering, dielectric |
| 相關次數: | 點閱:68 下載:1 |
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在液晶中摻雜中孔洞二氧化矽空心球(MPSHSs-LCs)中發現中孔洞二氧化矽空心球沒有聚集而且還有良好的分布,這結果不同於以往液晶內摻雜顆粒之情況。我們認為中孔洞二氧化矽空心球和液晶之間應有新的物理其應該有不同類型的錨定來自於中孔洞二氧化矽空心球的表面結構。為了瞭解該現象,我們在不同的溫度下進行MPSHSs-LC的散射測量,研究散射域和環境溫度之間的相關性,並討論其散射與中孔洞二氧化矽空心球濃度的相關性。此外,介電測定還進行協助研究的相轉變溫度的變化過程中,特別是在相變的溫度附近的實數和虛數部分可以反映出液晶相應鬆弛頻率與震盪模態。我們也同時測量了傳統的液晶散射型元件包含:多分子聚合物型液晶元件(PDLC),膽固醇型液晶元件(CLC),還有實心二氧化矽球液晶元件來佐證比對我們的想法。而平均場理論也可以用來解釋我們的實驗結果。平均場理論的假設可以很好地解釋T_ni(向列相 - 各向同性相兩者相變溫度)與中孔洞二氧化矽空心球大小和濃度的關係。我們發現具有體積小的中孔洞二氧化矽空心球具有較大的曲率因此對周圍的液晶影響力較大。
我們還通過散射實驗與示差掃描量熱儀(DCS)實驗中結果的相呼應其在相變點有一個透明向列態(Transparent-nematic)。在MPSHSs的情況下,該傾角是相當小的並是非常紊亂的狀態所以在較大尺寸或更高濃度的球比例下透明向列態會被抑制而不會出現。
Mesoporous silica hollow spheres (MPSHSs) doped in liquid crystals (MPSHSs-LCs) exhibits no aggregation and well-dispersed phenomenon, which reveals some new physics among MPSHSs and LCs. There should be different type of anchoring originated from the surface structure of MPSHSs. In order to realize the phenomenon, we perform the scattering measurement of MPSHSs-LCs with varied temperature to study the correlation between scattering domain and environment temperature, and discuss the dependence of the MPSHS concentration. Besides, dielectric measurement also performed to assist the study the phase transition during the temperature variation, especially in the temperature of phase transition. The real part and the image part of dielectrics result reflect the corresponding relaxation frequency of LCs and isotropic state, respectively. Polymer-dispersed in LCs (PDLCs), chiral LCs (CLCs) and solid silica spheres (SSSs) doped in LCs were also adopted in this work for comparison. We also use the mean field theory to explain our experimental results. The assumption of anisotropic anchoring in the mean field theory can well explain the relation between Tni (nematic-isotropic transition temperature) and the size and concentration of MPSHSs. MPSHS with small size has larger curvature and lead anchoring from the pores of MPSHSs to be strong and random. Thus, larger affected area around MPSHSs is formed at the case of small MPSHSs.
We also find the similar behavior in DCS experiments by scattering experiment. A dip appears in the scattering experiment with scan temperature. An opaque state exists on the period of nematic-isotropic transition, which is a transparent nematic state in DSC experiment. In the case of MPSHSs, the dip is quite small and is suppressed as the disorder state overcome the transparent nematic state at larger size or higher concentration. By using two series experiments with different kind of LC scattering devices, the correlation with MSPHS and scattering were confirmed.
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校內:2021-02-19公開