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系統識別號 U0026-1702201602115500
論文名稱(中文) 中孔洞氧化矽空心球在液晶之散射機制與溫度之關係
論文名稱(英文) The correlation between the scattering mechanism of mesoporous silica hollow sphere in LCs and temperature
校院名稱 成功大學
系所名稱(中) 物理學系
系所名稱(英) Department of Physics
學年度 104
學期 1
出版年 105
研究生(中文) 楊書寧
研究生(英文) Shu-Ning Yang
學號 L26021278
學位類別 碩士
語文別 英文
論文頁數 73頁
口試委員 指導教授-羅光耀
口試委員-林弘萍
口試委員-黃啟炎
中文關鍵字 液晶  穿透光譜  介電係數 
英文關鍵字 Liquid crystals  Light scattering  dielectric 
學科別分類
中文摘要 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。
英文摘要 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.
論文目次 Abstract I
摘要 II
致謝 II
CONTECT IV
List of tables VII
List of figures VIII
Chapter 1
INTRIDUCTION 1
1.1 Basic of Liquid crystals 1
1.1.1 Origin of Liquid Crystals 1
1.1.2 Nematic and Cholesteric liquid crystals 1
1.1.3 Anisotropic properties/ Birefringence 3
1.1.4 Order parameter for a cell 4
1.1.5 Elastic continuum theory 5
1.1.6 Surface anchoring force 6
1.2 Phase transition of liquid crystals 9
1.3 Porous materials doped in Liquid crystals 10
1.3.1 Electrical reorientation of liquid crystal molecules inside cylindrical pore 12
1.4 Particles doped in Liquid Crystals 14
1.5 Mesoporous silica hollow spheres 15
Chapter 2
Theory 18
2.1 Phase transition analyzed by DSC 18
2.2 Scattering mechanism 20
2.2.1 Light scattering of polymer-dispersed liquid crystal display 21
2.2.2 Light scattering of cholesteric liquid crystal 22
2.2.3 Light scattering of Mesoporous silica hollow sphere 22
2.2.4 Light scattering of non-porous silica surface sphere 24
2.2.5 Light scattering with temperature in NPs doped in LCs 25
2.3 Dielectric relaxation spectroscopy 27
2.3.1 The relaxation mode 28
2.3.2 Debye model 29
2.3.3 Real part of the dielectric constant 30
2.3.4 The image part of dielectric constant 31
2.3.5 Summary of dielectrics measurement 32
2.4 Mean field molecular theory 33
2.5. The analysis of MSHS-LCs by transmission, dielectrics measurement and Dilution effect…………………………………………………………………………..36
Chap 3
EXPERIMENT 37
3.1 MSPHSs preparation 37
3.2 Differential scanning calorimetry analysis 38
3.3 Light scattering 38
3.4 Dielectrics measurement 39
Chapter 4 40
RESULTS AND DISTRUTION 40
4.1 DSC Experiment 40
4.2 Light scattering 42
4.3 Dielectric spectroscopy 46
4.3.1 Image part of dielectric 46
4.3.2 Summary of MPSHSs in image part dielectrics measurement 56
4.4 Mean-field theory 67
Chapter 5
CONCLUDSION 69
Reference 71
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