We
present a method for fabricating photonic crystals (PCs) by
polymerization-induced microphase separation of block copolymers (BCPs).
Molecular weight of BCP for PCs is so large that it has been difficult
for conventional solution casting and annealing methods to complete
the microphase separation to form periodically ordered submicron structures.
Our method overcomes the difficulty by inducing the microphase separation
and transitions during the polymerization, when the molecular weight
of the BCPs is small enough for the microphase separation and transitions.
The microphase-separated structure is then enlarged while maintaining
the self-similarity. We succeeded in fabricating PCs with reflection
wavelength λm ≈ 1000 nm and a full width at
half-maximum Δλ = 0.05λm by living-radical
bulk block copolymerization of poly(methyl methacrylate)-block-polystyrene.
Blue phases (BPs) have received considerable attention as light shutters in the next generation of liquid crystal (LC) displays. However, no simple and efficient chiral dopant for induction of BPs of commercially available rodlike LC compounds has been reported. In this study, both (R) and (S) forms of novel chiral dopants were synthesized, showed extremely high helical twisting power values in nematic LC compounds, and induced stable BPs with a small amount of our chiral dopants (3-5 mol %). In enantiomeric excess controlled experiments, we found novel phenomena in their physical properties, such as generation of a metastable chiral nematic phase between an isotropic state and a BP.
A simple chiral dopant molecule (R)-1 with both rod- and arch-like units was prepared, and extremely large helical twisting powers (+123 to +228 μm(-1)) in nematic liquid crystal phases were achieved. We have demonstrated that the introduction of an arch-like unit in addition to rod-like units is highly effective in controlling the helical molecular alignment. As an application of the dopant, induction of blue phases by addition of a small amount of it was achieved.
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