| Summary: | 碩士 === 國立成功大學 === 物理學系 === 104 === 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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