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					Transmission Electron Microscopy




        Anne-Cecile Mortamet - 02 February 2010
                 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
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)
          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 T g
              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
        EXAMPLES of TEM images
                                      Phase separated structure of a
                                         polyurethane elastomer
                                                 sample
                                                  ACM
                                               April 2009



5µm




 SBS block copolymer structure   Typical TEM image of a SBS sample
             ADVANTAGES                       
• 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
              LIMITATIONS                     
• 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
                     WHERE?

                          You are here

    TEM Suite
Biomedical Science
   Department
                 CONTACTS

• Dr Svetomir Tzokov: s.b.tzokov@sheffield.ac.uk

• Mr Chris Hill: c.j.hill@sheffield.ac.uk>



   TRAINING REQUIRED FOR PREPARING AND IMAGING
                     SAMPLES
                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
Transmission Electron Microscopy


Ultra Cryomicrotomy for sample preparation



          Anne-Cecile Mortamet - 02 February 2010

				
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