Inducing Symmetry Breaking in Nanostructures: Anisotropic Stretch-Tuning Photonic Crystals

Abstract

We use elastically induced phase transitions to break the structural symmetry of self-assembled nanostructures, producing significantly modified functional properties. Stretching ordered polymer opals in different directions transforms the fcc photonic crystal into correspondingly distorted monoclinic lattices. This breaks the conventional selection rules for scattering from the crystal planes, yielding extra multiply scattered colors when the phase-breaking stretch is in specific directions. Scattering is spectroscopically tracked in real time as the samples distort, revealing a new phase transition that appears for <121>-oriented deformations.

Interplay of index contrast with periodicity in polymer photonic crystals

“…We note that all samples are mounted identically, with the shear processing direction in the same plane as source and detector, removing effects of anisotropy due to the orientation of the [111] lattice planes (see also Figure 1(a)). 19 In conclusion, we demonstrate how the light scattered from polymeric photonic crystals depends on the refractiveindex contrast. In this lower refractive-index contrast regime, the resonant Bragg reflection intensity varies linearly with Dn, in good agreement with a transfer-matrix model which incorporates the effects of disorder.…”

Functional Polymer Opals and Porous Materials by Shear‐Induced Assembly of Tailor‐Made Particles

“…In recent years, the melt‐shear organization technique has been further optimized by using a combination of extrusion, rolling and edge‐induced rotational shearing steps, providing access to monodomain bulk‐ordered photonic films on the multimeter length scale . Large‐area self‐supporting photonic crystal films could be obtained .…”

Multi-stimuli-responsive elastomeric opal films: processing, optics, and applications

“…5,7 When these films feature an elastomeric behavior, they also show remarkable color changes due to a precisely controlled lattice deformation by applying weak strain. [8][9][10]16 In recent years, this technique has been further optimized by using a combination of extrusion, rolling and edge-induced rotational shearing steps, providing access to mono-domain bulk-ordered films on the multi-meter length scale, while the structure-dependent iridescent colors were enhanced tremendously. 7,11,13 But this technique revealed one major drawback: it yields uncross-linked films which cannot be drawn reversibly.…”

“…[5][6][7] Because of their elastomeric properties, these films also show remarkable color changes under strain due to a controlled lattice deformation. [8][9][10] Meanwhile uniform samples on the multi-meter scale with mono-domain bulk-ordering of the submicrometer components can be prepared. [11][12][13] Additionally, the crystalline structure of these films can be made responsive to various external stimuli, either by modifying the beads correspondingly or by adding smart components.…”