趙治宇臺灣大學：物理研究所賴子暉Lai, Tzi-HueiTzi-HueiLai2007-11-262018-06-282007-11-262018-06-282005http://ntur.lib.ntu.edu.tw//handle/246246/54659近十年來，高解析度的比熱儀以及光反射的量測顯示液晶薄膜有逐層相變的趨勢。我們量測了44COOBC在SmA與HexB相變點附近的比熱行為，發現44COOBC與64COOBC存在許多相似的地方。由表面張力引發的相變行為，可能使得薄膜在低維度時產生與三維系統不同的行為。我們計算了相變所需熵的變化，發現熵與體積正比的關係可能在低維度會不存在。High-resolution heat capacity and optical-reflectivity measurements had been conducted near the smectic-A to hexatic-B transition in thin free-standing films of the liquid crystal compound 54COOBC and 64COOBC. It is surprise that dependence on film thickness of the integrated magnitude of the heat-capacity anomalies as the films undergo layer-by-layer transitions between 54COOBC and 64COOBC are different. Hence we measure 44COOBC at the same circumstance, and try to figure out how the effect on an alkyl in the liquid crystal compound.1 Introduction 1 1.1 What Is Liquid Crystal . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.2 Mesophase of Thermotropic Rod-like Liquid Crystals . . . .................. . . . . . . 3 2 Theoretical Background 7 2.1 Ising Model . . . . . . . . . . . . . . . . . . . . . . . . . ................................ . . . . . . 9 2.2 Correlation Length . . . . . . . . . . . . . . .............................. . . . . . . . . . . . . 9 2.3 Landau Mean Field Theory . . . . . . . . . . . . . . . . . . . . ........................ . 10 2.4 Renormalization Group . . . . . . . . . . ........................... . . . . . . . . . . . . . 12 2.4.1 Kadanoff ’s Argument . . . . . . . . . . . . . . . . . ..... ............................. . . 12 2.4.2 Renormalization Group . . . . . . . . . . . . . . . . . . . . ................................13 2.5 KTHNY- Model — Two Dimensional Melting Theory . . . . ............. 14 3 Heat Capacity and Optical Reflectivity Measurements 18 3.1 Heat Capacity Measurement System . . . . . . . . . . . . . . .................... . 18 3.2 Optical Reflectivity Measurement System . . . . . . . . . . .................. . . 25 4 History Background and The Motivation 28 4.1 KTHNY-Model In Experiments . . . . . . . . . . . . . . . . . . . . ......................... . 28 4.2 Interactions betweenmolecules of liquid crystals . . . ...................... . . . . . . . . 31 4.3 TheMotivation . . . . . . . . . . . . . . . ................................ . . . . . . . . . . . . . . . 32 5 Experimental Results and Discussions 36 5.1 Experimental Results . . . . . . . . . . . . . . . . . . . . . . . . ............................ . . . 36 5.2 Interactions betweenmolecules of n4COOBC . . . . . . . . . . ....................... . . . 38 5.3 Integrated Magnitude of Heat Capacity Anomalies . . . . . .................... . . . . . 39 6 Conclusions 461034134 bytesapplication/pdfen-US液晶薄膜臨界現象比熱free standing filmcritical pointheat capacitythesishttp://ntur.lib.ntu.edu.tw/bitstream/246246/54659/1/ntu-94-R92222022-1.pdf