A comparison between solid state and soft matter physics' The case for soft matter as core physics

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A comparison between solid state and soft matter
physics. The case for soft matter as core physics

• Mark Geoghegan
• Department of Physics and Astronomy

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Contents

• A consideration of IoP core physics
• The importance of core (second year) solid state
  physics
• Its contribution to years three and four
• The importance of soft matter
• How it builds on thermodynamics in years 1 and 2
• Why should we teach soft matter?
• How it might fit into a curriculum

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Core condensed matter physics

• Mechanical properties of matter to include
  elasticity and thermal expansion
• Inter-atomic forces and bonding
• Phonons and heat capacity
• Crystal structure and Bragg scattering
• Electron theory of solids to the level of simple
  band structure
• Semiconductors and doping
• Magnetic properties of matter

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Sheffield core 2nd year solids

• Crystallography
• Lattices, close packing, reciprocal lattice,
  Braggs law and the Laue condition
• Thermal properties and phonons
• Dulong-Petit, Einstein, and Debye models,
  phonons, crystal dynamics in one-dimension,
  thermal conductivity
• Electrons in solids
• Free electron model, thermionic and field emission

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Statistical mechanics in SSP

• Quantum mechanical oscillator
• Einstein model, a long proof
• Density of states
• Debye model
• Free electron model
• Fermi-Dirac probability distribution introduced
• Very time consuming to prove this distribution

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Soft condensed matter

• Intermolecular forces, viscoelasticity, the glass
  transition
• Phase separation in mixtures
• Polymers, gels
• Partial and liquid crystallinity
• Self-assembly in polymers, block copolymers, and
  surfactants

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Why should SCM be core?

• Because its important!
• UK manufacturing relies strongly on SCM
• Because its new!
• Condensed matter physics was not finished 50
  years ago!
• Because its interesting!
• It is not an abstract subject
• Because it uses thermodynamics heavily

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Thermodynamics
10 nm
Tie fibril

• Consider spinodal decomposition
• Use G U PV - TS
• To demonstrate ?G nRT(x1lnx1 x2lnx2)
• Conformational entropy of polymer chains
• Use ?S -3kBr2/2Na2 in rubber elasticity
• And again in crystallinity

Amorphous region between lamellae
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Some examples from SCM

• Behaviour of molecules in solvents
• Water is an important solvent
• Biological and environmental reasons why this is
  important
• Surfactant assemblies
• Bilayers and vesicles
• What does it take to create a delivery vehicle?

From D. E. Discher and A. Eisenberg Science 297
967-973 (2002)
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Gels

• Crosslinked polymers
• Hydrogels
• Wound dressings, Substrates for cell culture,
  Nappies etc.
• Vulcanized rubbers
• Tyres etc.
• Charles Goodyear provides an interesting
  chronicle of serendipity and determination

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Liquid crystallinity
Image from Liquid Crystalline Polymers 2nd ed. A.
M. Donald, A. H. Windle, S. Hanna CUP 2006

• Importance of LCDs is clear
• Twisted nematics and the Frederiks transition can
  be related to students
• Chirality and cholesteric liquid crystals
• Chirality can be explained in terms that students
  can understand

Enantiomer of thalidomide
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What should be core?

• Viscoelasticity
• That fluids can be solid like on short time
  scales is an important if unexpected concept
• Glass transition
• Not everything is crystalline!
• Not easy because not well understood anyway

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More core

• Phase separation
• Good use of fundamental thermodynamics
• Applies to a wide range of systems
• Alloy blends, polymers, solution-based systems
• Polymers
• Size of a polymer chain, some feeling about
  viscoelastic behaviour
• The importance of the Nobel prize for physics in
  1991, like that in 2007, should be understood

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Course and target students

• Third year physics students
• Second year SSP is crucial to semi-conductor
  behaviour
• Second year thermal physics is crucial to much
  (most) of SCM
• Scope to add other components in a module
• Self-assembly, crystallinity, rubbers and gels,
  colloidal dispersions, powders

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Can SCM fit into a curriculum?

• What should go?
• Physics is not getting any smaller
• However, many courses contain outdated material
• Very often in laboratory experiments
• Electronics need not be considered a crucial part
  of physics
• Can we dispose of some transferable skills?
• For example computer programming

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FTSE 100 companies (SCM)

• AstraZeneca
• BP
• GlaxoSmithKline
• ICI
• Johnson Matthey

• Reckitt Benckiser
• Royal Dutch Shell
• Smith and Nephew
• Unilever

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FTSE 100 companies (SSP)

• BAE Systems
• British Telecom
• Rolls Royce

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Conclusions

• SCM relies on a relatively straightforward basis
  of core thermodynamics and statistical physics
• that is otherwise taught for its own sake
• SCM could have been taught 20-25 years ago
• Maybe not before that it is a new subject
• Inclusion of soft matter is not going to happen
  spontaneously
• If SCM is important, this should be reflected in
  degree accreditation