Transmission Electron Microscopy

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Transmission Electron Microscopy
Anne-Cecile Mortamet - 02 February 2010
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WHY?

• To examine internal morphology of polymers from
  segmental to atomic level
• e.g. block copolymers, crystalline polymers,
  vesicles and polymers in solution
• Image contrast is produced through electron
  scattering by the atomic nuclei of the sample

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PRINCIPLE

• Beam of electrons transmitted through an ultra
  thin specimen
• Image formed, magnified and detected through a
  sensor (CCD camera)
• Contrast within the sample enhanced by the use of
  stains (heavy metal complexes selectively
  deposited in the sample e.g. RuO4, OsO4)

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Cryomicrotomy

• Microtome instrument used to cut thin specimen
  for microscopic study
• Cryomicrotome useful for polymers that are
  rubbery at room temperature possibility to cut
  at temperature below Tg

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Ultra CRYomicrotomy

• Cutting thin polymer sections by means of a
  glass knife (for trimming) and diamond knife (for
  cutting specimen up to 10nm thick) at low
  temperatures (up to -200oC)

SAMPLE CHAMBER
COOLING SYSTEM Liquid nitrogen dewar
Sample support MESH GRID
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EXAMPLES of TEM images
Phase separated structure of a polyurethane
elastomer sample ACM April 2009
SBS block copolymer structure
Typical TEM image of a SBS sample
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ADVANTAGES
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• TEM can magnify over 500 000 times
• It can resolve details as small as 1nm (better
  resolution than SEM)
• Smallest observable polymer structure crystal
  lattice

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LIMITATIONS
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• Extensive sample preparation to allow the
  specimen to be electron transparent (patience and
  time required!)
• Samples can be damaged by the electron beam
  irradiation they have to withstand high vaccum
• Small field of view restricts possibilities to
  get characteristics of the whole sample

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WHERE?
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CONTACTS

• Dr Svetomir Tzokov s.b.tzokov_at_sheffield.ac.uk
• Mr Chris Hill c.j.hill_at_sheffield.ac.ukgt

TRAINING REQUIRED FOR PREPARING AND IMAGING
SAMPLES
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REFERENCES

• 1 Transmission Electron Microscopy A Textbook
  for Materials Science, by David B. Williams
  (Author), C. Barry Carter
• 2 D. T. Grubb and L. C. Sawyer, Polymer
  Microscopy, 2nd ed., Chapman and Hall, London,
  1996
• 3 N. Reid, Ultramicrotomy, In A. Glauert
  (editor), Practical Methods in Electron
  Microscopy, Vol 3, North Holland Publishing Col,
  Amsterdam, 1974

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Transmission Electron Microscopy

• Ultra Cryomicrotomy for sample preparation

Anne-Cecile Mortamet - 02 February 2010