Numerično modeliranje interakcij na meji dveh tekočekristalnih medijev

Geršak, Rok (avtor), Čopar, Simon (mentor)

Tekoči kristali so zaradi svoje anizotropije, elastičnega odziva in topološko pogojenega obnašanja defektov nosilni medij v študijah preklopnih in samourejajočih se snovi. Raziskave teh snovi potekajo na številnih sistemih, med drugim na tekočekristalnih koloidih, tekočekristalnih suspenzijah itd., večji izziv pa predstavljajo sistemi, kjer sta v stiku dva mehka anizotropna medija, kot na primer v zmesi diskotičnih in kalamitičnih tekočih kristalov ali pa v zmesi termotropnih in liotropnih tekočih kristalov. Raziskave tovrstnih zmesi so v literaturi redke. V sklopu magistrskega dela smo z uporabo numeričnega modeliranja obravnavali stik dveh nematskih tekočekristalnih faz, pri katerem lahko pride do raznovrstnih interakcij med gradniki obeh snovi. Na sistemu, kjer holesterno kapljico obdaja zunanji nematik, smo preizkusili različne možne sklopitve med površino in ureditvenima parametroma obeh medijev ter raziskali obnašanje defektov in nastale strukture. Prav tako smo v pričakovanju reprodukcije neobjavljenih eksperimentalnih rezultatov raziskovalcev Instituta Jožef Stefan, preverili nekaj možnih kombinacij sklopitev na sistemu dveh nematskih kapljic, ki ju prav tako obkroža nematik. Dodatno pa smo na dveh testnih primerih demonstrirali možnost spreminjanja oblike kapljice.

• Jezik: Slovenski jezik
• Ključne besede: nematski tekoči kristali, holesterne kapljice, numerično modeliranje, površinsko sidranje, nematsko-nematsko sidranje, fazni model
• Vrsta gradiva: Magistrsko delo/naloga
• Tipologija: 2.09 - Magistrsko delo
• Organizacija: FMF - Fakulteta za matematiko in fiziko
• Leto izida: 2019
• PID: 20.500.12556/RUL-113385
• COBISS.SI-ID: 3373668
• Datum objave v RUL: 28.12.2019

GERŠAK, Rok, 2019, Numerično modeliranje interakcij na meji dveh tekočekristalnih medijev [na spletu]. Magistrsko delo. [Dostopano 19 maj 2025]. Pridobljeno s: https://repozitorij.uni-lj.si/IzpisGradiva.php?lang=slv&id=113385

Sekundarni jezik

• Jezik: Angleški jezik
• Naslov: Numerical modeling of interactions on the interface between two liquid crystal materials

Izvleček

Due to their anisotropy, elastic response and topological properties of defects, liquid crystals have a key role in studies of shape-switching and self-assembling materials. Such materials are being studied on several systems, among others on the liquid crystal colloids, liquid crystal suspensions etc. Systems where two anisotropic materials are in contact, like a mixture of discotic and calamitic liquid crystals or a mixture of thermotropic and lyotropic liquid crystals, remain a harder challenge and so studies of such mixtures are rare. In this master thesis, numerical modeling was used to investigate a contact region between two nematic phases, where diverse interactions among the constituent parts of both phases can occur. Various possible couplings between the surface and the order parameters of both phases were explored on a system of a cholesteric droplet surrounded by an outside nematic, and properties of resulting defect structures were studied. In anticipation of reproducing the unpublished experimental results from researchers of the Jožef Stefan Institute, different combinations of couplings were also explored on a system of two nematic droplets surrounded by an outside nematic. In addition to investigating the interface between the two nematic phases, a possibility of varying the droplet shape in simulation was also demonstrated on two test cases.

• Ključne besede: nematic liquid crystals, cholesteric droplets, numerical modeling, surface anchoring, nematic-nematic anchoring, phase field model