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Title:VPLIV TEMPERATURE IN OGRAJENOSTI NA DEBELINO SMEKTIČNIH PLASTI V TEKOČIH KRISTALIH
Authors:ID Jesenek, Dalija (Author)
ID KRALJ, SAMO (Mentor) More about this mentor... New window
Files:.pdf UNI_Jesenek_Dalija_2009.pdf (2,08 MB)
MD5: E03502B63C8693A59F3AF9B61E38FC31
PID: 20.500.12556/dkum/61c834d1-efc6-4f39-88df-e722cfeb36d6
 
Language:Slovenian
Work type:Undergraduate thesis
Organization:FNM - Faculty of Natural Sciences and Mathematics
Abstract:V diplomskem delu obravnavam vpliv temperature na debelino smektičnih plasti v SmA fazi. Tekoči kristali so bili neograjeni ali ograjeni v kontrolirano porozno steklo (Control Porous Glass ali CPG) z različnimi premeri luknjic. Kontrolirano porozno steklo je bilo neobdelano ali obdelano s silanom. Meritve debeline plasti so bile izvedene za tekoča kristala 8CB in 12CB, pri čemer je bila uporabljena metoda sipanja rentgenskih žarkov pod malim kotom (small angle x-ray scattering ali SAXS). Meritve tekočega kristala 12CB so bile izvedene v centru za makromolekularno kristalografijo (National Centre for Scientific Research »Demokritos«, Atene, Grčija), medtem ko so bili vzorci 8CB merjeni v Sinhrotronu »ELLETRA« v Trstu, Italija. Ureditev tekoče kristalnih molekul v vzorcih sem opisala s kombinacijo semi-mikrosopske in mezoskopske Landau-de Gennesovo teorije. Ugotovili smo, da se z nižanjem temperature debelina plasti za neograjena vzorca kvalitativno različno spreminja, in sicer se zmanjšuje za 8CB in povečuje za 12CB. Vzrok za to je v obliki molekule tekočega kristala. Na velikost fluktuacij in s tem deloma na debelino plasti vpliva tudi razlika v faznem prehodu med 8CB in 12CB. V tekočih kristalih omejenimi z neobdelanimi kontroliranimi poroznimi stekli smo v primerjavi z neomejenimi zasledili širjenje plasti. Dominantni mehanizmi, odgovorni za takšno vedenje, so površinski spominski efekti. V obdelanem kontroliranem poroznem steklu pa se debelina plasti glede na neomejene vzorce ni bistveno spremenila. Nazadnje sem z Landau-de Gennesovo metodo razložila vzrok za razliko v faznih prehodih med tekočima kristaloma 8CB in 12CB.
Keywords:smektični tekoči kristali, Landau-de Gennesova teorija, metoda sipanja rentgenskih žarkov pod malim kotom (SAXS), spominski efekti
Place of publishing:Maribor
Publisher:[D. Jesenek]
Year of publishing:2009
PID:20.500.12556/DKUM-11515 New window
UDC:53(043.2)
COBISS.SI-ID:17110280 New window
NUK URN:URN:SI:UM:DK:ADHFHKAS
Publication date in DKUM:11.09.2009
Views:3297
Downloads:217
Metadata:XML DC-XML DC-RDF
Categories:FNM
:
JESENEK, Dalija, 2009, VPLIV TEMPERATURE IN OGRAJENOSTI NA DEBELINO SMEKTIČNIH PLASTI V TEKOČIH KRISTALIH [online]. Bachelor’s thesis. Maribor : D. Jesenek. [Accessed 18 April 2025]. Retrieved from: https://dk.um.si/IzpisGradiva.php?lang=eng&id=11515
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Secondary language

Language:English
Title:INFLUENCE OF TEMPERATURE AND CONFINEMENT ON LIQUID CRYSTALS SMECTIC LAYER SPACING
Abstract:This graduation thesis discusses temperature variations of a smectic layer thickness in the SmA phase. Liquid crystals were enclosed or not into a controlled porous glass (CPG) with various void diameters. The controlled porous glass was either silane treated or not. Measurements of layer thickness were performed for liquid crystals 8CB and 12CB where the small angle x-ray scattering technique (SAXS) was used. The measurements of 12CB took place in the Centre for Crystallography of Macromolecules (National Centre for Scientific Research »Demokritos«, Athens, Greece), meanwhile the 8CB samples were measured at Synchrotron »ELETTRA« in Trieste, Italy. The liquid crystals molecules arrangement in samples has been described by the combination of semi-microscopic and mezzoscopic Landau-de Gennes theory. We found out that on decreasing the temperature in the bulk samples the layer thickness has qualitatively different behavior, furthermore it is decreasing for 8CB and increasing for 12CB. Reason for this is the liquid crystal molecular features. The difference in phase transition between 8CB and 12CB influence on fluctuations and with this partly on layer thickness as well. In comparison with unlimited liquid crystals, the liquid crystals confined to non-treated controlled porous glasses have been found to dilate their layers significantly. The dominant mechanisms responsible for such behaviour are surface memory effects. In treated controlled porous glass the layer thickness has not suffered any significant changes. Finally I involved the Landau-de Gennes theory to give explanation to the reason for difference in phase transitions between liquid crystals 8CB and 12CB.
Keywords:smectic liquid crystals, Landau-de Gennes theory, small angle x-ray scattering (SAXS), memory effects


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