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Questions and Answers
What phase of matter do liquid crystals exhibit properties between?
What phase of matter do liquid crystals exhibit properties between?
- Liquid and gas
- Solid and gas
- Gas and plasma
- Solid and liquid (correct)
All mesogens are liquid crystals.
All mesogens are liquid crystals.
False (B)
What shape are the molecules in liquid crystals typically?
What shape are the molecules in liquid crystals typically?
Rod-shaped or disc-shaped
Liquid crystal molecules prefer to align ______ to each other due to strong intermolecular attraction.
Liquid crystal molecules prefer to align ______ to each other due to strong intermolecular attraction.
What is a key characteristic of nematic liquid crystals?
What is a key characteristic of nematic liquid crystals?
What is the term for the direction of preferred orientation in a liquid crystal?
What is the term for the direction of preferred orientation in a liquid crystal?
Thermotropic liquid crystals are classified based on ______.
Thermotropic liquid crystals are classified based on ______.
Which of the following is a type of thermotropic liquid crystal?
Which of the following is a type of thermotropic liquid crystal?
What defines a cholesteric liquid crystal?
What defines a cholesteric liquid crystal?
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Study Notes
Introduction to Liquid Crystals
- Liquid crystals are substances that exhibit a phase of matter with properties of both liquids and solids.
- Examples include LCD TVs and alarm clocks.
Types of Liquid Crystals
- Thermotropic Liquid Crystals: Formed by temperature changes and exist within a specific temperature range.
- Calamatic L.C.: Rod-shaped molecules further classified into Nematic and Smectic liquid crystals.
- Discotic L.C.: Disc-shaped molecules.
- Lyotropic Liquid Crystals: Formed by changes in solvent concentration.
Liquid Crystal Properties
- Molecules are rod-shaped or disc-shaped.
- They are anisotropic (different properties in different directions).
- Molecules have strong dipole moments.
- Liquid crystal molecules tend to align parallel due to strong intermolecular attraction.
- A typical Liquid Crystal molecule consists of:
- A central rigid part known as a mesogen (generally aromatic).
- Flexible ends (usually aliphatic groups).
Liquid Crystal Phases (Mesophases)
- Defined by the level of ordering in the molecules.
- Positional Order: Refers to the arrangement of molecules in a lattice.
- Orientational Order: Refers to the alignment of molecules in a specific direction.
- Both types of order can be short-range (between nearby molecules) or long-range (extending to larger dimensions).
Nematic Liquid Crystals
- Word origin: Derived from the Greek word “Nema” meaning "thread."
- Characteristics:
- No positional order.
- Possess orientational order.
- Molecules have an elongated rod-like shape.
- Do not have a layered structure.
- Flow like normal liquids with low viscosity.
- Forme...
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