Lecture 01, 2

• What is the concept of surface and interfacial tension?

  It describes the energy at interfaces.
• Why are surfactants important in pharmaceutical science?

  They modify surface properties and enhance solubility.
• What factors affect the critical micelle concentration (CMC) of a surfactant?

  Hydrophilic head type, salt content, and temperature.
• What do interfacial properties describe?

  The behaviour of materials at an interface.
• What is an interface?

  Where one material meets another without miscibility.
• How do interfacial properties differ from bulk properties?

  They may be very different from bulk material properties.
• What happens when water is poured on glass?

  Water forms bonds with silanol units.
• How is the affinity of a liquid for a solid investigated?

  By examining the contact angle of a liquid drop.
• What does a small contact angle indicate?

  Strong intermolecular interaction and spreading.
• What is wettability?

  The ability of a liquid to spread on a surface.
• What are cohesive forces?

  Attractive forces between molecules of the same type.
• What are adhesive forces?

  Attractive forces between different types of molecules.
• What is surface tension?

  Energy required to increase the surface area of a liquid.
• How does temperature affect surface tension?

  Surface tension decreases with increasing temperature.
• Why does adding salt to water increase surface tension?

  Salt ions interfere with hydrogen bonding.
• Why is mercury's surface tension high?

  Metallic bonds are stronger than hydrogen bonds.
• What causes interfacial tension?

  Mismatched adhesion and cohesion at interfaces.
• What is Young's equation used for?

  Relating contact angle and surface tensions.
• What does the work required to expand a surface area represent?

  The surface free energy of the interface.
• What shape do liquids assume due to surface tension?

  A spherical shape, like droplets.
• What are surfactants?

  Surface active agents with hydrophilic and hydrophobic parts.
• What happens to surfactants at the CMC?

  Micelles start to form above this concentration.
• How do surfactants reduce interfacial tension?

  By replacing water/oil molecules at the interface.
• What is the role of micelles in drug solubilisation?

  They enhance solubility of poorly water-soluble drugs.
• What is the HLB number?

  A measure of surfactant's amphiphilic nature.
• What does an increase in hydrophobic chain length do to CMC?

  It decreases the CMC.
• How does temperature affect CMC for non-ionic surfactants?

  Increasing temperature decreases CMC and increases micelle size.
• What happens to the solubility of drugs below CMC?

  Solubility does not improve below CMC.
• What is the effect of ionic surfactants on CMC with increased salt content?

  CMC decreases due to charge shielding.
• What is the effect of surfactants on disperse systems?

  They improve formulation and stability of medicines.
• What are common applications of surfactants?

  Wetting, solubilising, emulsifying, and foaming agents.
• What is the significance of surfactants in mRNA vaccines?

  They enhance solubility and stability of formulations.
• What happens to the amount of lidocaine dissolved when surfactants are added?

  Surfactants enhance lidocaine solubility in water.
• What are the applications of surfactants in pharmaceuticals?

  • Enhance drug solubility
  • Improve surface wetting
  • Stabilise disperse systems
  • Act as wetting, solubilising, emulsifying, and foaming agents
• What factors affect the critical micelle concentration (CMC) of surfactants?

  • Hydrophilic head type
  • Salt content
  • Temperature
  • Chain length of hydrophobic and hydrophilic components
• What is the relationship between surfactants and micelles?

  • Surfactants form micelles above CMC
  • Micelles enhance solubility of hydrophobic drugs
  • Surfactants orient at interfaces to reduce surface tension
• What are the strengths and weaknesses of surfactants in pharmaceuticals?

  Strengths:

  • Enhance drug solubility
  • Stabilise formulations
  • Improve surface wetting

  
  

  Weaknesses:

  • Can be irritants
  • May cause allergic reactions