Journal
ACS APPLIED MATERIALS & INTERFACES
Volume 12, Issue 5, Pages 5265-5273Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acsami.9b11928
Keywords
dichroic molecules; surface topography; liquid crystal networks; fingerprint; electric field
Funding
- European Research Council under ERC [66999]
- 4TU.HighTech Materials research program 'New Horizons in designer materials'
- NVVO VENI grant [15135]
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Surface topography variations of liquid crystal networks in their functional coatings provide unique properties in these systems. Chiral-nematic polymer coatings self-organize in a fingerprint texture with the molecular helices parallel to the substrate with alternating domains of molecular units with parallel and perpendicular director orientation as controlled by the concentration of a reactive chiral additive. Driven by surface-tension differences and altered by anisotropic polymerization shrinkage, the coating may form hills and valleys hundreds of nanometers in size with different molecular alignment. The director orientation in the corrugations could be controlled by monomer diffusion during polymerization. Polymerization in the presence of a dichroic dye gives topographic elevations in which the molecules are oriented along the normal. Polymerization by means of a dichroic photoinitiator gives topographic elevations in which the molecules align parallel to the surface. By balancing the monomer diffusion and anisotropic polymerization shrinkage, relatively flat surfaces are also achieved. The different surfaces exhibit distinct topographical deformations when subjected to external stimuli, such as an AC electric field. This method can be universally extended to LC polymers with other alignment configurations.
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