Iridescent Colors from Films Made of Polymeric Core-Shell Particles

Bioinspired Color Elastomers Combining Structural, Dye, and Background Colors

Organisms that alter body color undergo color change in response to environmental variations and stimuli by combining chromatophores that develop colors by various mechanisms. Inspired by their body color changes, we can develop sensors and optical materials that change colors in response to multiple stimuli, such as mechanical and light stimuli. In this study, we report on bioinspired composite elastomers that exhibit various color changes as the pigment color, structural color, and background color change. These composite elastomers exhibit structural colors due to their fine structures in which fine silica particles form colloidal crystals, and the structural colors reversibly change as the elastomers elongate. Furthermore, photochromic dyes can reversibly change color depending on the wavelength of irradiated light when they are introduced to the composite elastomers. Since the structural color is one of the three primary colors of light and the pigment color is the color that corresponds to the three primary colors of a pigment, each color becomes vivid when the background color is black or white. Thus, we clarify that the composite elastomers exhibit various color changes due to the combination of structural color change in response to the mechanical stimulus, pigment color change in response to light irradiation, and background color change.

Optical Properties of the Self-Assembling Polymeric Colloidal Systems

In the last decade, optical materials have gained much interest due to the high number of possible applications involving path or intensity control and filtering of light. The continuous emerging technology in the field of electrooptical devices or medical applications allowed the development of new innovative cost effective processes to obtain optical materials suited for future applications such as hybrid/polymeric solar cells, lasers, polymeric optical fibers, and chemo- and biosensing devices. Considering the above, the aim of this review is to present recent studies in the field of photonic crystals involving the use of polymeric materials.

Fluorescence properties of photonic crystals doped with perylenediimide

This study aims to present the fabrication of colloidal photonic crystals (PC) with increased fluorescence properties. The use of a highly fluorescent perylenediimide derivate (PDI) during the soap-free emulsion polymerization of styrene-acrylic acid resulted in monodisperse core-shell particles which allowed the fabrication of PC films. The properties of the hybrid material were studied in comparison with hybrid materials obtained by impregnation of films with chromophore solutions. In both cases an increase of the fluorescence response was observed in addition to a blue shift for the PDI core particles, proving the incorporation of the dye inside the copolymer particles.

Soft Core–Hard Shell Silicone Hybrid Nanoparticles Synthesized by Miniemulsion Polymerization: Effect of Silicone Content and Crosslinking on Latex Film Properties

Composite nanoparticles consisting of ‘soft’ silicone oil and ‘hard’ polyacrylate with core–shell morphology were obtained by a one-step synthesis via the miniemulsion process. Various parameters, i.e. the viscosity and amount of the silicone, the surfactant content, the (co)monomers affecting the particle size and morphology were studied. With an optimum hydrophilicity of the polymer shell, composite particles possessing a well-defined core–shell morphology were obtained as determined by transmission electron microscopy. The fully encapsulated silicone oil (40 wt-%) in a slightly crosslinked polyacrylate shell showed good film formation as revealed by atomic force microscopy. The ability to highly confine silicone oil in the composite film could clearly be evaluated from contact angle measurements. By finely changing the crosslink concentration in the polymeric shell, tunable hydrophobic properties of films cast from silicone core–polyacrylate shell latexes could be achieved. In addition, the high thermal resistance and excellent water-resistant properties of the film were shown by thermal gravimetric analysis and water swelling determination. These composite latexes are presented as new alternatives for practical utility in waterborne coatings.

Tough photonic crystals fabricated by photo-crosslinkage of latex spheres

A general method to enhance the mechanical properties and solvent resistance of photonic crystals (PCs) has been demonstrated. This is carried out by the crosslinkage of latex spheres via photopolymerization of acrylamide (AAm) infiltrated among them. The crosslinked PAAm enhances the interaction among latex spheres of the PCs film, and contributes to the improvement of mechanical strength and solvent resistance. The result provides a simple approach to make tough PCs films by photo-crosslinkage, and can be extended to a wide variety of materials, will be of great importance for the practical application of PCs.

Covalent and physical cross-linking of photonic crystals with 10-fold-enhanced chemomechanical stability

We report opal photonic crystals that are self-assembled from functional polymer particles. We randomly copolymerized functional side-chain monomers containing motifs that form homodimers or heterobridges. These include ether or methylene bridges, hydrazone bridges, acids for anhydride formation, low- T g copolymers or physical cross-links by hydrogen bonds and/or polarity. To generate particles that are monodisperse, spherical, and functionalized, we combined emulsifier-free synthesis with swelling synthesis steps. Laser diffraction from centimeter-sized beams, white-light interferometry, and atomic force microscopy demonstrates symmetry and homogeneity across the entire crystal without the loss of interstitial volume. Compared to the stability of nonfunctional particles, the stability of the crystal against immersion in water and isopropanol was enhanced from 10 to a perfect 100%. One of the successful approaches (methylene bridges from N-methylolmethacrylamid) is triggered by thermal activation, but as shown, this is operative far from the trivial regime of sintering. We demonstrate successful infiltration with and solvation of a laser-polymerizable resin, thus enabling the processing of 3D photonic waveguide structures.