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Prof R C Evans

Soft materials such as polymers, gels, foams, colloids, emulsions and liquid crystals touch every aspect of our daily lives. These materials cannot be simply described as pure states of matter, such as gases, liquids or solids, but instead exhibit properties reminiscent of a given state depending on the timescale at which they are probed. Soft materials are at the forefront of many modern technologies in the information and communication, energy, biotechnology, food, pharmaceutical and cosmetics sectors.

The course is designed to enable you to understand the fundamental properties and behaviour of soft materials in terms of the interactions between their component parts. We will focus on colloidal dispersions – systems in which small droplets or particles of one material are dispersed in a continuous medium of another material. The role of intermolecular forces and surface energy in controlling the stability of the colloidal system will first be unravelled. We will then consider solution- and gas-phase syntheses of different types of nanoparticles, before discussing their properties and potential applications as colloidal dispersions (solid in liquid). We will finish by considering the formation and stabilisation of foams (gas in liquid) and emulsions (liquid in liquid).

This course complements the polymer topics covered in IA, IB, part II and part III (M6), although attendance at the latter is not a prerequisite for this course.

This lecture course will cover:

  • Intermolecular forces and self-assembly (1 lecture): Recap on thermal equilibrium, intermolecular forces (London, van der Waals, electrostatic, hydrogen bonding, hydrophobic effects), diffusion, aggregation and assembly.
  • Colloidal materials: characteristics and stability (2 lectures): Classes of colloidal systems and their properties, time-dependent stability of colloidal dispersions, role of surface energy and interparticular interactions on colloidal stability, DVLO theory, electrical double layers, steric repulsion.
  • Synthesis, applications and characterisation of colloids/nanoparticles (2 lectures): Bottom-up versus top-down approaches, solution-phase synthesis (homogeneous condensation, sol-gel, solvothermal), gas-phase synthesis (spray pyrolysis). Classes of materials considered include metal and metal oxide nanoparticles, quantum dots, magnetic nanoparticles, polymer nanoparticles. Characterisation techniques: dynamic light scattering and zeta potential.
  • Foams and emulsions (1 lecture): Introduction to surfactants and their properties (surface tension, self-assembly), formation and stabilisation of foams (gas/liquid), La Place equation, emulsions: classes, preparation and stabilisation, role of emulsifiers.