Liquid crystals MCQs With Answer

Liquid crystals MCQs With Answer is an essential resource for B. Pharm students aiming to master the structure, properties, and pharmaceutical applications of liquid crystalline systems. This concise guide covers thermotropic and lyotropic mesophases, molecular orientation, order parameters, birefringence, dielectric anisotropy, and methods like POM, DSC, XRD useful in characterization. Emphasis is on formulation roles in drug delivery, controlled release, topical systems, stability, and analytical evaluation. Keywords include liquid crystals, B. Pharm, mesophases, nematic, smectic, cholesteric, drug delivery, and optical properties. Now let’s test your knowledge with 50 MCQs on this topic.

Q1. What defines a liquid crystal state?

• A completely disordered isotropic fluid
• A crystalline solid with no molecular mobility
• An intermediate state with partial molecular order and fluidity
• A gas-like phase with high compressibility

Correct Answer: An intermediate state with partial molecular order and fluidity

Q2. Which type of liquid crystal is most commonly studied in pharmaceutical formulations for drug delivery?

• Thermotropic lyotropic hybrids
• Thermotropic liquid crystals
• Lyotropic liquid crystals
• Cholesteric solids

Correct Answer: Lyotropic liquid crystals

Q3. Which mesophase is characterized by molecules arranged in layers and some positional order?

• Nematic
• Smectic
• Cholesteric
• Isotropic

Correct Answer: Smectic

Q4. What is the primary distinguishing feature of a nematic liquid crystal?

• Long-range positional order in three dimensions
• Layered molecular stacking with tilt
• Long-range orientational order without positional order
• Molecules forming closed vesicles

Correct Answer: Long-range orientational order without positional order

Q5. Which technique is most useful for observing textures and birefringence in liquid crystals?

• Scanning electron microscopy (SEM)
• Polarized optical microscopy (POM)
• Nuclear magnetic resonance (NMR)
• Mass spectrometry

Correct Answer: Polarized optical microscopy (POM)

Q6. In lyotropic liquid crystals, what primarily governs phase formation?

• Temperature only
• Concentration of amphiphiles and solvent
• Crystal lattice parameters
• Atmospheric pressure

Correct Answer: Concentration of amphiphiles and solvent

Q7. What is a common pharmaceutical application of liquid crystalline phases?

• Improving tablet hardness exclusively
• Controlled and sustained drug release
• Gas sterilization
• Reducing API melting point only

Correct Answer: Controlled and sustained drug release

Q8. Which mesophase exhibits a helical arrangement of molecules and selective Bragg reflection of light?

• Nematic
• Smectic A
• Cholesteric (chiral nematic)
• Columnar

Correct Answer: Cholesteric (chiral nematic)

Q9. What does the order parameter (S) in liquid crystals measure?

• Degree of translational order
• Degree of orientational order
• Molecular weight distribution
• Viscosity at a given shear rate

Correct Answer: Degree of orientational order

Q10. Which property of liquid crystals is exploited in electro-optic devices and can be relevant for drug release modulation?

• Dielectric anisotropy
• High melting point
• Low surface tension
• Isotropic conductivity

Correct Answer: Dielectric anisotropy

Q11. Which calorimetric technique is commonly used to determine phase transition temperatures of liquid crystals?

• Thermogravimetric analysis (TGA)
• Differential scanning calorimetry (DSC)
• Isothermal titration calorimetry (ITC)
• Bomb calorimetry

Correct Answer: Differential scanning calorimetry (DSC)

Q12. What is a mesogen?

• A surfactant that forms micelles only
• The molecular unit responsible for liquid crystalline behavior
• A polymer chain used in tablets
• A type of solvent used for LC preparation

Correct Answer: The molecular unit responsible for liquid crystalline behavior

Q13. Which of the following is a lyotropic mesophase relevant in topical formulations?

• Isotropic solution
• Cubic and hexagonal phases
• Orthorhombic crystals
• Vitreous solids

Correct Answer: Cubic and hexagonal phases

Q14. Which parameter directly correlates with optical birefringence in liquid crystals?

• Order parameter and molecular polarizability anisotropy
• Density alone
• Surface tension only
• pH of the medium

Correct Answer: Order parameter and molecular polarizability anisotropy

Q15. What role can liquid crystalline nanoparticles play in oral drug delivery?

• Decrease bioadhesion entirely
• Enhance solubility and protect labile drugs
• Act as taste masking by chemical reaction
• Serve only as fillers in tablets

Correct Answer: Enhance solubility and protect labile drugs

Q16. The Frederiks transition is associated with:

• Phase separation in polymer blends
• Reorientation of LC director under an external field
• Crystallization from melt
• Micelle fusion in solution

Correct Answer: Reorientation of LC director under an external field

Q17. Which analytical method provides information on layer spacing in smectic and lamellar liquid crystals?

• Small-angle X-ray scattering (SAXS)
• Infrared spectroscopy (IR)
• Ultraviolet-visible spectroscopy (UV-Vis)
• Gas chromatography (GC)

Correct Answer: Small-angle X-ray scattering (SAXS)

Q18. Which factor most strongly influences the formation of lyotropic liquid crystalline phases from lipids?

• The lipid molecular geometry and hydration level
• The altitude of preparation
• The presence of heavy metals
• The ambient noise level

Correct Answer: The lipid molecular geometry and hydration level

Q19. In the context of liquid crystals, what is a “director”?

• The temperature at which LC melts
• The average orientation vector of molecules in a domain
• A laboratory instrument for LC synthesis
• A regulatory guideline for LC use

Correct Answer: The average orientation vector of molecules in a domain

Q20. Birefringence in liquid crystals arises because:

• Molecules are chiral in all cases
• Refractive index depends on molecular orientation
• LCs have ionic conductivity
• LCs are fully isotropic

Correct Answer: Refractive index depends on molecular orientation

Q21. Which liquid crystalline phase is frequently associated with high viscosity and anisotropic flow?

• Nematic with low order
• Smectic and columnar phases
• Isotropic liquids
• Gaseous phases

Correct Answer: Smectic and columnar phases

Q22. Which of the following is a common surfactant used to form lyotropic liquid crystals for drug delivery?

• Sodium lauryl sulfate (SLS)
• Monoolein and phytantriol
• Polytetrafluoroethylene
• Sucrose

Correct Answer: Monoolein and phytantriol

Q23. In liquid crystal formulations, what is a primary stability concern for APIs?

• Gas evolution
• Phase transitions altering release kinetics
• Loss of tablet whiteness
• Uncontrolled polymer crosslinking

Correct Answer: Phase transitions altering release kinetics

Q24. Which measurement gives information about molecular mobility and order in liquid crystals at the atomic level?

• Dynamic light scattering (DLS)
• Nuclear magnetic resonance (NMR)
• Thermogravimetric analysis (TGA)
• Polarography

Correct Answer: Nuclear magnetic resonance (NMR)

Q25. Columnar liquid crystals are characterized by:

• Molecules forming stacked columns with two-dimensional order
• Complete three-dimensional crystalline order
• Only isotropic micellar structures
• A single uniform refractive index

Correct Answer: Molecules forming stacked columns with two-dimensional order

Q26. Which property is essential when designing LC-based topical formulations for skin delivery?

• High volatility
• Biocompatibility and appropriate rheology
• Electrical conductivity equal to skin
• Opacity to visible light

Correct Answer: Biocompatibility and appropriate rheology

Q27. Chiral dopants in nematic LCs are used to:

• Increase isotropic viscosity
• Induce a helical twist and form cholesteric phases
• Make the material non-responsive to fields
• Reduce molecular weight

Correct Answer: Induce a helical twist and form cholesteric phases

Q28. What effect does temperature have on thermotropic liquid crystals?

• No effect; only concentration matters
• Drives mesophase transitions between ordered and isotropic states
• Only changes color but not phase
• Eliminates molecular anisotropy permanently

Correct Answer: Drives mesophase transitions between ordered and isotropic states

Q29. Which rheological behavior is often exhibited by lyotropic liquid crystalline gels?

• Newtonian flow with constant viscosity
• Shear-thinning and viscoelasticity
• Purely elastic solid behavior
• Negative viscosity

Correct Answer: Shear-thinning and viscoelasticity

Q30. In formulating LC-based drug carriers, which factor helps control release rate?

• Molecular packing and mesophase geometry
• Color of the formulation
• Ambient sound frequency
• Presence of inert gases

Correct Answer: Molecular packing and mesophase geometry

Q31. Which analytical tool can map nanoscale structures in cubic and hexagonal LCs for drug formulations?

• Optical microscopy without polarization
• Transmission electron microscopy (TEM) with cryo-prep
• pH meter
• UV-Vis spectrophotometer

Correct Answer: Transmission electron microscopy (TEM) with cryo-prep

Q32. What is a common challenge when incorporating hydrophobic drugs into lyotropic LC systems?

• Complete loss of drug potency
• Ensuring proper partitioning into hydrophobic domains
• Excessive crystallization of water
• Gas formation within the phase

Correct Answer: Ensuring proper partitioning into hydrophobic domains

Q33. Dielectric anisotropy positive in a liquid crystal means:

• Molecules align perpendicular to applied electric field
• Molecules align parallel to applied electric field
• Material has no dipole moment
• Phase becomes isotropic instantly

Correct Answer: Molecules align parallel to applied electric field

Q34. Which structural feature of amphiphiles favors formation of inverted (reverse) lyotropic mesophases?

• Large hydrophilic head and small hydrophobic tail
• Large hydrophobic tail and relatively small headgroup
• Completely symmetric di-head structures
• No hydrophobic part at all

Correct Answer: Large hydrophobic tail and relatively small headgroup

Q35. Which property makes liquid crystalline polymers useful in sustained-release matrices?

• High solubility in water
• Ordered domains providing diffusion barriers
• Instant disintegration in gastric fluid
• Complete chemical inertness under all conditions

Correct Answer: Ordered domains providing diffusion barriers

Q36. Which test helps evaluate mechanical stability and flow properties of LC gels?

• Rheological oscillation and shear tests
• Thin-layer chromatography (TLC)
• Flame photometry
• Mercury intrusion porosimetry

Correct Answer: Rheological oscillation and shear tests

Q37. How can pH influence lyotropic liquid crystal systems in drug formulations?

• No influence; pH is irrelevant
• Alter ionization of amphiphiles and change mesophase behavior
• Only affects color, not structure
• Makes the system combustible

Correct Answer: Alter ionization of amphiphiles and change mesophase behavior

Q38. Which of the following is an indicator of phase purity and uniformity in LC formulations?

• Single, reproducible POM texture and SAXS pattern
• Presence of multiple random colors under visible light
• Random changes in pH over time
• Formation of gas bubbles on standing

Correct Answer: Single, reproducible POM texture and SAXS pattern

Q39. Amphiphilic block copolymers can form which liquid crystalline structures useful for drug encapsulation?

• Only crystalline salts
• Micellar and lyotropic mesophases including cubic phases
• Gaseous foams
• Metallic alloys

Correct Answer: Micellar and lyotropic mesophases including cubic phases

Q40. Which safety/regulatory consideration is particularly relevant for LC excipients in pharmaceuticals?

• Their melting point relative to refrigerators
• Toxicity, biocompatibility, and residual solvent limits
• Their color matching packaging
• Their electrical conductivity rating

Correct Answer: Toxicity, biocompatibility, and residual solvent limits

Q41. What does SAXS peak spacing reveal about lyotropic mesophases?

• Only chemical composition
• Characteristic repeat distances and symmetry of the mesophase
• Viscosity directly
• pH of the sample

Correct Answer: Characteristic repeat distances and symmetry of the mesophase

Q42. Which component often acts as a stabilizer for LC nanoparticles in suspension?

• Hydrophobic solvents only
• Surface-active polymers or surfactants providing steric/electrostatic stabilization
• Heavy metals
• Pure crystalline salts

Correct Answer: Surface-active polymers or surfactants providing steric/electrostatic stabilization

Q43. How does molecular chirality affect liquid crystalline behavior?

• Always prevents mesophase formation
• Can induce chiral nematic (cholesteric) phases with selective reflection
• Only changes melting point but not mesophase type
• Makes the material completely isotropic

Correct Answer: Can induce chiral nematic (cholesteric) phases with selective reflection

Q44. Which measurement is best for assessing water uptake and hydration behavior of lyotropic LC formulations?

• Gravimetric swelling studies and water sorption assays
• Atomic absorption spectroscopy
• Gas chromatography
• pH indicator strips only

Correct Answer: Gravimetric swelling studies and water sorption assays

Q45. What is the primary mechanism of drug release from lamellar (layered) liquid crystalline matrices?

• Bulk erosion without diffusion control
• Diffusion through aqueous layers and interlamellar spaces
• Catalytic cleavage by metal ions
• Spontaneous combustion

Correct Answer: Diffusion through aqueous layers and interlamellar spaces

Q46. Which experimental condition can induce defects and textures in LC films important for sensors?

• Applied shear, substrate interactions, and temperature gradients
• Complete absence of light only
• Magnetic resonance imaging
• Presence of high concentrations of inert gases only

Correct Answer: Applied shear, substrate interactions, and temperature gradients

Q47. What is the effect of adding salt (electrolyte) to some lyotropic LC systems?

• No effect at any concentration
• Can screen headgroup charges and shift mesophase boundaries
• Makes the system combustible
• Instantly converts them to solids

Correct Answer: Can screen headgroup charges and shift mesophase boundaries

Q48. Which LC property can be tuned to create stimuli-responsive drug delivery systems?

• Color only
• Phase behavior responsive to temperature, pH, or electric field
• Radioactivity
• Inert gas solubility exclusively

Correct Answer: Phase behavior responsive to temperature, pH, or electric field

Q49. In quality control of LC formulations, which attribute is critical to monitor during storage?

• Phase integrity and absence of unwanted phase transitions
• Number of bubbles under high vacuum only
• The formulation’s smell only
• Magnetic susceptibility only

Correct Answer: Phase integrity and absence of unwanted phase transitions

Q50. Which statement best summarizes why B. Pharm students should study liquid crystals?

• They are only of academic interest with no pharmaceutical relevance
• LC knowledge enables rational design of advanced drug delivery and topical systems
• LCs replace all excipients in formulations
• LCs are only used in electronics and not pharmaceutics

Correct Answer: LC knowledge enables rational design of advanced drug delivery and topical systems

G S Sachin

I am a Registered Pharmacist under the Pharmacy Act, 1948, and the founder of PharmacyFreak.com. I hold a Bachelor of Pharmacy degree from Rungta College of Pharmaceutical Science and Research. With a strong academic foundation and practical knowledge, I am committed to providing accurate, easy-to-understand content to support pharmacy students and professionals. My aim is to make complex pharmaceutical concepts accessible and useful for real-world application.

Mail- Sachin@pharmacyfreak.com