[PHYPHARM-FINALS] THE LIQUID CRYSTALLINE STATE

Mesophase

A state of matter that exists between the conventional solid and liquid phases.

Mesophase

It is characterized by partial molecular order and fluidity.

Partial molecular order and fluidity

Mesophase is characterized by?

Mesophase

This intermediate phase is most commonly observed in liquid crystals, amphiphilic systems, and certain polymers.

• Liquid crystals

• Amphiphilic systems

• Certain Polymers

Mesophase is most commonly observed in?

Solid

Mesophase: Molecular Behavior

Molecules are tightly packed in a fixed, ordered arrangement.

Liquids

Mesophase: Molecular Behavior

Molecules move freely with no long-range order.

Directional or Positional Order

In mesophases, molecules exhibit this order while retaining mobility, creating a hybrid behavior.

Mesogens

Mesophase is also known as?

Mesogens

This is a compound that displays liquid crystal properties.

• Rigid

• Organic

• Possess strong dipoles and easily polarizable groups

• Elongated and rectilinear in shape

What are the four characteristics of Mesophases (Mesogens)?

Thermotropic

What are the two types of liquid crystals by origin?

Thermotropic

Types of Liquid Crystals by Origin

Formed by changing temperature (heating of solids).

Thermotropic

Exhibit phase transitions with heat.

Thermotropic

Common in synthetic materials.

Nematic, Smectic, and Cholesteric Phases

What are the four phases of Thermotropic?

• LCD screens

• Organic compounds

• Polymers

Thermotropic can be observed in?

Lyotropic

Types of Liquid Crystals by Origin

Formed by changing concentration of solvent (usually water).

Lyotropic

Found in biological systems.

Lyotropic

Self-assemble into mesophases.

Temperature and Concentration

Lyotropic is sensitive to both?

• Lipid bilayers

• Soaps

• Drug delivery systems

Lyotropic can be found/observed in?

Lyotropic liquid crystals

These are used in lipid-based drug delivery systems (e.g., cubic and hexagonal phases).

Lipid-based drug delivery systems

Lyotropic liquid crystals are used in?

Bioavailability and controlled release

Lyotropic liquid crystals enhances?

Biological membranes

Lyotropic liquid crystals mimic ____, making them ideal for topical and oral formulations.

Topical and oral formulations

Lyotropic liquid crystals mimic biological membranes, making them ideal for these type of formulations.

Friedrich Reinitzer in 1888

The first recorded observation of a thermotropic liquid crystal was made by?

Cholesteryl benzoate

Reinitzer first observed the thermotropic liquid crystal when he heated this chemical compound.

145 degrees celsius

At this temperature, the solid formed a turbid liquid (the thermotropic liquid crystal, which only became clear, to give the conventional liquid state at 179 degrees celsius.

179 degrees celsius

To give the conventional liquid state at what temperature?

Smectic and Nematic

What are the two types of liquid crystals?

Smectic

This type of liquid crystal is characterized as soap or grease-like.

Nematic

This type of liquid crystal is characterized as thread-like.

Smectic State

In this state, molecules are mobile in two directions and can rotate about one axis.

Nematic State

In this state, the molecules again rotate only about one axis but are mobile in three dimensions.

Cholesteric Crystals

A third type of liquid crystals exists but may be considered a special case of the nematic state.

Nematic

Molecules align along a common axis (long-range orientational order).

• “Thread-like”

• No positional layering.

• Fluid-like behavior.

• LCD screens

• Nematic polymers

Examples of Nematic.

Nematic

This is used in anisotropic drug diffusion systems; responsive to electric fields for smart delivery.

Smectic

Molecules form layers with positional order.

• “Soap-like/Grease-like”

• May have tilt or rotation within layers and is more ordered than nematic.

• Thermotropic liquid crystals

• Transdermal patches

Examples of Smectic.

Smectic

Enables layered drug release; useful in topical formulations and sustained delivery systems.

Smectic

This is the most important in pharmaceutical area.

Cholesteric

Chiral nematic phase with helical molecular arrangement.

• Reflects light selectively (color changes)

• Sensitive to temperature.

Cholesteric

Chiral nematic, a special type of nematic.

Temperature

Cholesteric is sensitive to?

• Cholesteryl esters

• Temperature-sensitive paints

Examples of Cholesteryl.

Cholesteryl

Applied in biosensors, smart packaging, and visual indicators for temperature-sensitive drugs.

Nematic

Smectic

Cholesteric