Liquid Crystals Lecture Review

These flashcards review key concepts related to liquid crystals, including definitions, phases, properties, and applications.

Liquid Crystals (LCs)

Matter in a state that has properties between conventional liquid and solid crystal.

Thermotropic Liquid Crystals

Liquid crystals that change phases in response to temperature variations.

Lyotropic Liquid Crystals

Liquid crystals whose phases are influenced by the concentration of solvents.

Phase Diagram

A chart that shows the phases present at different temperatures and concentrations.

Nematic Phase

A phase where molecules exhibit long-range orientational order but no positional order.

Smectic Phase

Liquid crystals that form well-defined layers and can slide over one another.

Cholesteric Liquid Crystals

A chiral phase characterized by helical ordering of molecules.

Birefringence

The optical property of a material that causes light to split into two rays with different velocities.

Phase Transition

The change from one phase of matter to another, such as nematic to isotropic.

Schlieren Texture

Texture seen in nematic liquid crystals under polarized light, characterized by dark brushes.

Optical Properties of Liquid Crystals

Liquid crystals refract light differently depending on their orientation and composition.

LCD (Liquid Crystal Display)

A flat panel display technology that uses liquid crystals to modulate light.

Order Parameter (S)

A measure of the degree of order in a system; S=0 indicates no order, S=1 indicates full order.

Helical Order

The twisting arrangement of molecules in cholesteric phases.

Components/Compositions

The elements or compounds present in a liquid crystal system, affecting its phase behavior.

Director

The preferred direction of molecular orientation in a liquid crystal.

Anisotropic Materials

Materials that have different properties in different directions, such as liquid crystals.

External Perturbations

Factors like temperature and electric fields that can change the state or properties of liquid crystals.

Colloidosomes

Structures formed from colloids that can exhibit liquid crystal properties.

Phase Weight Fractions

The relative proportions of different phases present in a material at equilibrium.

Twist Grain Boundaries

Defects in smectic phases that result in a helical structure.

Optical Response to Electrical Field

The change in the orientation of liquid crystal molecules when subjected to an electric field.