Structures of constrained blue phases: modelling and simulationWang, Shun (Avtor) Žumer, Slobodan (Mentor) Ravnik, Miha (Komentor) cholesteric liquid crystalblue phasesdisclinationshalf-skyrmion latticessurface anchoringsurface patterningconfinementdislocationsnumerical simulationStructures of liquid crystalline blue phases (BPs) confined by patterned surfaces of different geometries are investigated using numerical simulation based on the Landau-de Gennes phenomenological approach. In the first part of the thesis, BPII sandwiched between a pair of parallel confining surfaces with specifically designed patterns is studied. Patterned confining surfaces are made by imposing different types of surface anchoring in different regions of the surfaces. Directed by the surface patterns, quasi-two-dimensional half-Skyrmion lattices are formed. Specifically, we observe the formation of square and triangular lattices of half-Skyrmions. These lattices of the swirling skyrmion textures are interspersed with singular -1/2 or -1 line defects which also constitute quasi-two-dimensional regular lattices. The demonstrated structures may have potential for photonic applications, including as waveplates and two-dimensional photonic crystals. In the second part of the thesis, edge and screw dislocation structures in confined BPI and BPII are extensively studied numerically. This work is inspired by the analogies between BPs and solid crystals\textemdash they both exhibit three-dimensional lattice structures. Dislocation structures are induced by confining BPs inside specifically designed boundaries, which are made by appropriately distorting the bulk BP unit cells or by patterning the molecular anchoring on the confining surfaces. Various dislocations with Burgers vector magnitude equaling one or two times the unit cell size are obtained. Networks of the defect lines and the double twist cylinders are analyzed. Unveiling these dislocation structures deepens the understanding of BP structures under confinement. Finally, our work is a contribution to designing and stabilizing complex birefringent layer profiles in BPs under various constraints.20192019-02-20 07:45:02Doktorsko delo/naloga106351sl