Fluoropolymer-Containing Opals and Inverse Opals by Melt-Shear Organization

Robust and Durable Photonic Crystal with Liquid-Repellent Property for Self-Cleaning Coatings and Structural Colored Textiles

Photonic crystal coatings with unique structural colors and self-cleaning properties have been providing an efficient way for substrate coloration. However, the enhancement of the robustness and durability of structural colored coatings to meet the requirements in diverse environments remains a challenging task. Here, to realize the application of photonic crystal films under various kinds of conditions, we present a poly(fluoroalkyl acrylate)-based colloidal photonic crystal (fCPC) coating. Fluorinated core-interlayer-shell (FCIS) colloidal particles of polystyrene (PS) core, poly(methyl methacrylate) (PMMA) interlayer, and poly(fluoroalkyl acrylate-ethyl acrylate-butyl acrylate) (P(FA-EA-BA)) shell copolymers have been first prepared by a stepwise emulsion polymerization. fCPCs with self-supporting property, reprocessing ability, friction resistance, as well as excellent wettability and liquid-repellent properties are successfully obtained via the bending-induced ordering technique (BIOT). When applied in antifouling applications, the fCPC film exhibits resistance against various oil and inorganic liquids. Furthermore, the fCPC coatings demonstrate their durability under outdoor conditions by maintaining stable color appearances during rainy and sunny conditions. Additionally, an electronic product adhered with the fCPC coatings is presented, which exhibits a surface that remains clean even after prolonged usage in comparison to the conventional CPC coating. Structural colored textiles with enhanced stability and functionalized liquid-repellent properties are achieved through a one-step process using FCIS particles. Therefore, the developed self-cleaning and comprehensive fCPC coatings capable of withstanding diverse conditions may open up new avenues for the advancement of structural coloration in decoration, vehicle, textile, and building.

Fluoropolymer: A Review on Its Emulsion Preparation and Wettability to Solid-Liquid Interface

In the preparation of a superamphiphobic surface, the most basic method is to reduce the surface free energy of the interface. The C-F bond has a very low surface free energy, which can significantly change the wettability of the solid-liquid interface and make it a hydrophobic or oleophobic, or even superamphiphobic surface. Based on the analysis of a large number of research articles, the preparation and application progress in fluoropolymer emulsion were summarized. After that, some corresponding thoughts were put forward combined with our professional characteristics. According to recent research, the status of the fluoropolymer emulsion preparation system was analyzed. In addition, all related aspects of fluoropolymer emulsion were systematically classified in varying degrees. Furthermore, the interaction between fluoropolymer structure and properties, especially the interaction with nanomaterials, was also explored. The aim of this review is to try to attract more scholars' attention to fluorocarbon interfacial materials. It is expected that it will make a certain theoretical and practical significance in the preparation and application of fluoropolymer.

Embedding Photoacids into Polymer Opal Structures: Synergistic Effects on Optical and Stimuli-Responsive Features

Opal films with their vivid structural colors represent a field of tremendous interest and obtained materials offer the possibility for many applications, such as optical sensors or anti-counterfeiting materials. A convenient method for the generation of opal structures relies on the tailored design of core-interlayer-shell (CIS) particles. Within the present study, elastomeric opal films were combined with stimuli-responsive photoacids to further influence the optical properties of structurally colored materials. Starting from cross-linked polystyrene (PS) core particles featuring a hydroxy-rich and polar soft shell, opal films were prepared by application of the melt-shear organization technique. The photoacid tris(2,2,2-trifluoroethyl) 8-hydroxypyrene-1,3,6-trisulfonate (TFEHTS) could be conveniently incorporated during freeze-drying the particle dispersion and prior to the melt-shear organization. Furthermore, the polar opal matrix featuring hydroxylic moieties enabled excited-state proton transfer (ESPT), which is proved by spectroscopic evaluation. Finally, the influence of the photoacid on the optical properties of the 3-dimensional colloidal crystals were investigated within different experimental conditions. The angle dependence of the emission spectra unambiguously shows the selective suppression of the photoacid's fluorescence in its deprotonated state.

Cross-Linking Strategies for Fluorine-Containing Polymer Coatings for Durable Resistant Water- and Oil-Repellency

Functional coatings for application on surfaces are of growing interest. Especially in the textile industry, durable water and oil repellent finishes are of special demand for implementation in the outdoor sector, but also as safety-protection clothes against oil or chemicals. Such oil and chemical repellent textiles can be achieved by coating surfaces with fluoropolymers. As many concerns exist regarding (per)fluorinated polymers due to their high persistence and accumulation capacity in the environment, a durable and resistant coating is essential also during the washing processes of textiles. Within the present study, different strategies are examined for a durable resistant cross-linking of a novel fluoropolymer on the surface of fibers. The monomer 2-((1,1,2-trifluoro-2-(perfluoropropoxy)ethyl)thio)ethyl acrylate, whose fluorinated side-chain is degradable by treatment with ozone, was used for this purpose. The polymers were synthesized via free radical polymerization in emulsion, and different amounts of cross-linking reagents were copolymerized. The final polymer dispersions were applied to cellulose fibers and the cross-linking was induced thermally or by irradiation with UV-light. In order to investigate the cross-linking efficiency, tensile elongation studies were carried out. In addition, multiple washing processes of the fibers were performed and the polymer loss during washing, as well as the effects on oil and water repellency were investigated. The cross-linking strategy paves the way to a durable fluoropolymer-based functional coating and the polymers are expected to provide a promising and sustainable alternative to functional coatings.

Mechanochromism in Structurally Colored Polymeric Materials

Mechanochromic effects in structurally colored materials are the result of deformation-induced changes to their ordered nanostructures. Polymeric materials which respond in this way to deformation offer an attractive combination of characteristics, including continuous strain sensing, high strain resolution, and a wide strain-sensing range. Such materials are potentially useful for a wide range of applications, which extend from pressure-sensing bandages to anti-counterfeiting devices. Focusing on the materials design aspects, recent developments in this field are summarized. The article starts with an overview of different approaches to achieve mechanochromic effects in structurally colored materials, before the physical principles governing the interaction of light with each of these materials types are summarized. Diverse methodologies to prepare these polymers are then discussed in detail, and where applicable, naturally occurring materials that inspired the design of artificial systems are discussed. The capabilities and limitations of structurally colored materials in reporting and visualizing mechanical deformation are examined from a general standpoint and also in more specific technological contexts. To conclude, current trends in the field are highlighted and possible future opportunities are identified.

Compression-Responsive Photonic Crystals Based on Fluorine-Containing Polymers

Fluoropolymers represent a unique class of functional polymers due to their various interesting and important properties such as thermal stability, resistance toward chemicals, repellent behaviors, and their low refractive indices in comparison to other polymeric materials. Based on the latter optical property, fluoropolymers are particularly of interest for the preparation of photonic crystals for optical sensing application. Within the present study, photonic crystals were prepared based on core-interlayer-shell particles focusing on fluoropolymers. For particle assembly, the melt-shear organization technique was applied. The high order and refractive index contrast of the individual components of the colloidal crystal structure lead to remarkable reflection colors according to Bragg’s law of diffraction. Due to the special architecture of the particles, consisting of a soft core, a comparably hard interlayer, and again a soft shell, the resulting opal films were capable of changing their shape and domain sizes upon applied pressure, which was accompanied with a (reversible) change of the observed reflection colors as well. By the incorporation of adjustable amounts of UV cross-linking agents into the opal film and subsequent treatment with different UV irradiation times, stable and pressure-sensitive opal films were obtained. It is shown that the present strategy led to (i) pressure-sensitive opal films featuring reversibly switchable reflection colors and (ii) that opal films can be prepared, for which the written pattern—resulting from the compressed particles—could be fixed upon subsequent irradiation with UV light. The herein described novel fluoropolymer-containing photonic crystals, with their pressure-tunable reflection color, are promising candidates in the field of sensing devices and as potential candidates for anti-counterfeiting materials.

Temperature-Induced Coloration and Interface Shell Cross-Linking for the Preparation of Polymer-Based Opal Films

The formation of colloidal crystals and their use as photonic materials are of high interest for various technologies in the field of sensing applications, as templates, absorber materials, catalysts, and membranes. In this study, core-shell particles consisting of a cross-linked poly(methyl methacrylate) core featuring a (polyacrylonitrile-co-styrene) shell are synthesized by starved-feed emulsion polymerization. The resulting particles are investigated with respect to size and monodispersity, as well as the core-to-shell ratio, by means of dynamic light scattering and transmission electron microscopy. Optimized particle sizes are 218 nm for the cores and 276 nm for the core-shell particles. For the formation of highly ordered and free-standing opal films, the particles are processed by the melt-shear organization technique. The resulting films show angle-dependent reflection colors, while reflected colors can be tailored by the design of the core-shell particles. As a focus of this work, polyacrylonitrile as part of the copolymer particle shell is advantageously used both for particle opal film stabilization and for tailoring the reflection colors of the opal films. It is shown that the cyclization reactions at the interface of the particles and within the matrix material significantly influence the optical properties of the opal films upon thermal treatment at 240 °C and for different heat holding times. For instance, the change of color can be simply set from red to blue upon defined thermal treatment conditions. Via this convenient protocol, brilliant reflection colors can thus be obtained based on the insights into the structure-property relationships of the underlying particle architectures and interface reactions. The scalable opal films will pave the way to functional colored materials as interesting candidates for a manifold of sensing applications and temperature-responsive polymeric materials.