Order by Design: Blueprinting Liquid Crystal Director Fields <em>Surfaces, Fields, and Self-Assembly for Orientational Order</em> Yvonne Zagzag

Format:

Book

Thesis/Dissertation

Author/Creator:

Zagzag, Yvonne, author.

Contributor:

University of Pennsylvania. Physics and Astronomy., degree granting institution.

Language:

English

Subjects (All):

0605.

0606.

0607.

0611.

Local Subjects:

0605.

0606.

0607.

0611.

Physical Description:

1 electronic resource (156 pages)

Contained In:

Dissertations Abstracts International 87-07B

Place of Publication:

Ann Arbor : ProQuest Dissertations and Theses, 2025

Language Note:

English

Summary:

Liquid crystals are highly responsive to external stimuli, surface anchoring, and geometric confinement. Their orientational order can be deliberately molded by designed physical constraints. This thesis investigates how magnetic fields and interfacial interactions can be used to blueprint orientational order in soft matter systems, revealing how the local alignment of liquid crystal molecules dictates structure and function. A theoretical framework for nematic elasticity, surface anchoring, and optical anisotropy is first developed. This links continuum models to experimental observations from polarized optical microscopy. Building on this foundation, the first study shows that ferromagnetic microstructures embedded in a nematic liquid crystal concentrate and reshape magnetic fields. As a result, they locally reorient the liquid crystal director. Experimental and computational analyses reveal how magnetic and elastic torques interact. This produces spatially tunable alignment and field-directed texturing. The second major study investigates ligand-mediated orientation and defect interactions of nanoparticle rafts at the liquid crystal-air interface. In hybrid-aligned nematic films, well-defined pre-tilt and defect landscapes couple to the orientation of ligand-capped nanoparticles. This work uses optical modeling, birefringence mapping, and imaging to identify bistable synclinic and anticlinic raft configurations. It reveals defect-mediated switching dynamics and shows how nanoparticle assemblies can stretch or pin disclination loops. These findings establish nanoparticle rafts as both probes and actuators of orientational order. The third study presents simulations of helical smectic filaments. These simulations model how partially coalesced ribbons twist into helices and form networks. The computational framework reproduces experimental birefringence textures. These studies show that orientational order in liquid crystals can be engineered by integrating magnetic, geometric, and interfacial effects. Combining experimental and theoretical approaches, this work provides a framework for designing bespoke director fields

Notes:

Advisors: Osuji, Chinedum O.; Kamien, Randall D. Committee members: Blake, Cullen H.; Sako, Masao; Stebe, Kathleen J.; Lacaze, Emmanuelle

Source: Dissertations Abstracts International, Volume: 87-07, Section: B.

Ph.D. University of Pennsylvania 2025

Vendor supplied data

Local Notes:

School code: 0175

ISBN:

9798276006161

Access Restriction:

Restricted for use by site license