Trapping Structural Coloration by a Bioinspired Gyroid Microstructure in Solid State

In theory, gyroid photonic crystals in butterfly wings exhibit advanced optical properties as a result of their highly interconnected microstructures. Because of the difficulties in synthesizing artificial gyroid materials having periodicity corresponding to visible wavelengths, human-made visible gyroid photonic crystals are still unachievable by self-assembly. In this study, we develop a physical approachtrapping of structural coloration (TOSC)through which the visible structural coloration of an expanded gyroid lattice in a solvated state can be preserved in the solid state, thereby allowing the fabrication of visible-wavelength gyroid photonic crystals. Through control over the diffusivity and diffusive distance for solvent evaporation, the single-molecular-weight gyroid block copolymer photonic crystal can exhibit desired structural coloration in the solid state without the need to introduce any additives, namely, evapochromism. Also, greatly enhanced reflectivity is observed arising from the formation of porous gyroid nanochannels, similar to those in butterfly wings. As a result, TOSC facilitates the fabrication of the human-made solid gyroid photonic crystal featuring tunable and switchable structural coloration without the synthesis to alter the molecular weight. It appears to be applicable in the fields of optical communication, energy, light-emission, sensors, and displays

Trapping Structural Coloration by a Bioinspired Gyroid Microstructure in Solid State

In theory, gyroid photonic crystals in butterfly wings exhibit advanced optical properties as a result of their highly interconnected microstructures. Because of the difficulties in synthesizing artificial gyroid materials having periodicity corresponding to visible wavelengths, human-made visible gyroid photonic crystals are still unachievable by self-assembly. In this study, we develop a physical approachtrapping of structural coloration (TOSC)through which the visible structural coloration of an expanded gyroid lattice in a solvated state can be preserved in the solid state, thereby allowing the fabrication of visible-wavelength gyroid photonic crystals. Through control over the diffusivity and diffusive distance for solvent evaporation, the single-molecular-weight gyroid block copolymer photonic crystal can exhibit desired structural coloration in the solid state without the need to introduce any additives, namely, evapochromism. Also, greatly enhanced reflectivity is observed arising from the formation of porous gyroid nanochannels, similar to those in butterfly wings. As a result, TOSC facilitates the fabrication of the human-made solid gyroid photonic crystal featuring tunable and switchable structural coloration without the synthesis to alter the molecular weight. It appears to be applicable in the fields of optical communication, energy, light-emission, sensors, and displays

Trapping Structural Coloration by a Bioinspired Gyroid Microstructure in Solid State

In theory, gyroid photonic crystals in butterfly wings exhibit advanced optical properties as a result of their highly interconnected microstructures. Because of the difficulties in synthesizing artificial gyroid materials having periodicity corresponding to visible wavelengths, human-made visible gyroid photonic crystals are still unachievable by self-assembly. In this study, we develop a physical approachtrapping of structural coloration (TOSC)through which the visible structural coloration of an expanded gyroid lattice in a solvated state can be preserved in the solid state, thereby allowing the fabrication of visible-wavelength gyroid photonic crystals. Through control over the diffusivity and diffusive distance for solvent evaporation, the single-molecular-weight gyroid block copolymer photonic crystal can exhibit desired structural coloration in the solid state without the need to introduce any additives, namely, evapochromism. Also, greatly enhanced reflectivity is observed arising from the formation of porous gyroid nanochannels, similar to those in butterfly wings. As a result, TOSC facilitates the fabrication of the human-made solid gyroid photonic crystal featuring tunable and switchable structural coloration without the synthesis to alter the molecular weight. It appears to be applicable in the fields of optical communication, energy, light-emission, sensors, and displays

Flexible or Robust Amorphous Photonic Crystals from Network-Forming Block Copolymers for Sensing Solvent Vapors

Large-area and flexible amorphous photonic crystals (APCs) featuring interconnected network microstructures are fabricated using high-molecular-weight polystyrene-<i>block</i>-poly­(methyl methacrylate) (PS–PMMA) block copolymers. Kinetically controlled microphase separation combining with synergistic weak incompatibility gives rise to short-range-order network microstructures, exhibiting noniridescent optical properties. Solubility-dependent solvatochromism with distinct responses to various organic solvent vapors is observed in the network-forming APC film. By taking advantage of photodegradation of the PMMA block, nanoporous network-forming films were prepared for subsequent template synthesis of robust SiO₂- and TiO₂-based APC films through sol–gel reaction. Consequently, refractive index contrast of the APC film was able to be manipulated, resulting in intensely enhanced reflectivity and increased response rate for detecting solvent vapor. With the integration of self-assembly and photolithography approaches, flexible and robust network-forming APC films with well-defined photopatterned textures are carried out. This can provide a novel means for the design of photopatterned organic or inorganic APC films for sensing solvent vapors

Flexible or Robust Amorphous Photonic Crystals from Network-Forming Block Copolymers for Sensing Solvent Vapors

Large-area and flexible amorphous photonic crystals (APCs) featuring interconnected network microstructures are fabricated using high-molecular-weight polystyrene-<i>block</i>-poly­(methyl methacrylate) (PS–PMMA) block copolymers. Kinetically controlled microphase separation combining with synergistic weak incompatibility gives rise to short-range-order network microstructures, exhibiting noniridescent optical properties. Solubility-dependent solvatochromism with distinct responses to various organic solvent vapors is observed in the network-forming APC film. By taking advantage of photodegradation of the PMMA block, nanoporous network-forming films were prepared for subsequent template synthesis of robust SiO₂- and TiO₂-based APC films through sol–gel reaction. Consequently, refractive index contrast of the APC film was able to be manipulated, resulting in intensely enhanced reflectivity and increased response rate for detecting solvent vapor. With the integration of self-assembly and photolithography approaches, flexible and robust network-forming APC films with well-defined photopatterned textures are carried out. This can provide a novel means for the design of photopatterned organic or inorganic APC films for sensing solvent vapors

Live Templates of a Supramolecular Block Copolymer for the Synthesis of Ordered Nanostructured TiO₂ Films via Guest Exchange

In this work, we introduce a facile method based on host–guest chemistry to synthesize a range of nanostructured TiO₂ materials using supramolecular templates of a dendron-jacketed block copolymer (DJBCP). The DJBCP is composed of amphiphilic dendrons (4′-(3,4,5-trido­decyl­oxy­benzoyl­oxy)­benzoic acid, TDB) selectively incorporated into a P4VP block of polystyrene-<i>block</i>-poly­(4-vinyl­pyridine) (PS-<i>b</i>-P4VP) via hydrogen bonding. The PS-<i>b</i>-P4VP host acts as a structure-directing template, while the guest molecules (TDB) assist the self-assembly nanostructures and zone-axis alignment, resulting in the nanostructured template of vertically oriented cylinders formed via successive phase transformations from <i>Im</i>3̅<i>m</i> to <i>R</i>3̅<i>m</i> to <i>P</i>6<i>mm</i> upon thermal annealing in the doctor-blade-cast film. The guest molecules subsequently direct the titania precursors into the P4VP domains of the templates via supramolecular guest exchange during immersion of the film in a designated precursor solution containing a P4VP-selective solvent. The subsequent UV irradiation step leads to the formation of PS-<i>b</i>-P4VP/​TiO₂ hybrids. Finally, removal of the host template by calcination leaves behind mesoporous channels and makes sacrifices to be a carbon source for carbon-doping TiO₂ materials. Various TiO₂ nanoarchitectures, namely, vertical and wiggly micrometer-length channels, inverse opals, fingerprint-like channels, heterogeneous multilayers, and nanotubes, have been fabricated by highly tunable DJBCP nanostructures