Micrograph 639 and full record
- Micrograph no
- 639
- Brief description
- Twist-escaped loops in the liquid crystalline polymer MBBA
- Keywords
- defect , escape, liquid crystalline polymer (LCP), loop, polymer , shear
- Categories
- Polymer
- System
- Liquid crystalline polymer
- Composition
- MBBA
- Standard codes
- Reaction
- Processing
- shear rate =5 s-1, sample thickness =500 microns, room temperature
- Applications
- The molecules in a LCP mesophase can be steered by external fields; a property used in display technology. Alignment is also exploited in high strength fibres like Kevlar and mouldable Vectra
- Sample preparation
- Technique
- Cross-polarised light microscopy
- Length bar
- 200 μm
- Further information
- Once a weak shear flow is applied on the nematic liquid, there is a sudden and strong increase in the defect density. At a certain shear rate, the equilibrium density is reached after a while through the creation and annihilation of defects. This in-situ observation enables the study of a wide range of dynamic disclination behaviours during shear, such as disclination-joining, loop-contracting, loop-stretching and loop-breaking. The loops in this image result from type 1 disclinations 'escaping' into three-dimensions by twist.
- Contributor
- Prof A H Windle
- Organisation
- Department of Materials Science and Metallurgy, University of Cambridge
- Date
- 03/10/02
- Licence for re-use
- Attribution-NonCommercial-ShareAlike 4.0 International
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