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DoITPoMS Micrograph Library Full Record for Micrograph 645
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Full Record for Micrograph 645

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Micrograph no
645
Brief description
An image of a single crystal alkane
Keywords
alkane, lamella Link to MATTER Glossary entry for lamella, polymer Link to MATTER Glossary entry for polymer, single crystal
Categories
Polymer
System
Alkane
Composition
C294H590
Standard codes
Reaction
Processing
The sample was crystallized at 68 degrees C for 16 hours
Applications
These materials provide ideal model systems for understanding the behaviour of synthetic polymers, as they are available in lengths bridging the gap between behaviour typically associated with polymers (such as chain folding) and that of small molecules. However, in contrast to fractionated materials, they are strictly monodiperse, allowing effects of polydispersity to separated from those of chain length.
Sample preparation
Technique
Transmission electron microscopy (TEM)
Length bar
2.4 μm
Further information
In high polymers, although it is commonly observed that crystalline lamellae grown from the melt thicken after initial crystallization, in crystallization from dilute solution it is generally found that the single crystals grown maintain the thickness with which they originally grew unless they are annealed above their original crystallization temperature. In contrast to this, it has been found that ultra long alkanes grown in dilute solution will thicken at the crystallization temperature from an initial (integer) folded form to more stable, thicker, integer folded or extended forms, given sufficient time. The thickening behaviour of C294H590 between three times folded and twice folded has been studied. This TEM image is of a thickened lozenge shaped crystal, clearly showing the preferential thickening of sector boundaries to form a 'picture frame' outer rim, and the dendritic structure of the central region.
Contributor
J Hobbs
Organisation
Scanning Probe Microscopy Group, Bristol University
Date
03/10/02
Licence for re-use
DoITPoMS standard terms of use