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Cross-linked poly(ethyl acrylate-co-methyl methacrylate) (P(EA-MMA)) nanoparticles were prepared by soap-free emulsion polymerization. Size of the isolated nanoparticles in various organic solvents was largely swollen when the solubility parameter of the solvent was similar to that for P(EA-MMA). Well-ordered colloidal crystal assembly film of the...
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Citations
... On the one hand, they are often used as a drug carrier, [10][11][12] with a 100-500 nm size range. On the other hand, size monodisperse polymeric nanoparticles are used to elaborate colloidal crystal films through their ability to diffract visible light, [13][14][15] where particle size is selected depending on the desired wavelengths to be diffracted. ...
Poly(methyl methacrylate) (PMMA) colloidal particles are nowadays extensively used in several applications and more specifically in nanotechnology. Challenges are focused on the green synthesis process leading to size‐controlled particles. In the present work, PMMA particles were successfully synthesized using tandem acoustic emulsification in water without organic solvent, and cross‐linkers. 2,2′‐azobis(2‐methylpropionamidine) dihydrochloride (AIBA) or ammonium persulfate (APS), were used as initiators. Parameters leading to size control were clearly identified. Consequently, the cooling rate of the solution after polymerization time appears dominating. Particle size distribution was monodispersed for both initiators. A nonionic surfactant, Tween 20, was also added, leading to a decrease in size particle and an increase in synthesis yield. Depending on the chemical groups provided by the initiator, PMMA particles appear negatively or positively charged. These charges located on the particle surface led to stable particle dispersion by limiting aggregation phenomena. Tunable surface charge was confirmed across the elaboration of coatings only made of PMMA particles, using conventional techniques wherein charged species are needed (Layer‐by‐Layer assembly and electrophoretic deposition). PMMA particles were also labelled using fluorescent dyes. Fluorescein and Nile Blue A were loaded during the polymerization process to ensure a homogeneous distribution of the dyes within the particles.
... Compared with photonic crystals fabricated by top-down processes, such as lithography and selective etching [8,9], colloidal photonic crystals have a significant advantage in that their optical stopband can readily be set in the visible-light region through a self-assembly process using submicron-sized colloids. Therefore, they are expected to find extensive use in various photonic applications and devices such as optical filters, lasers [10,11], sensors [12][13][14][15][16][17][18][19], color pigments [20,21], and displays [22,23]. For these applications, however, the control of the optical stopband, which is characterized by the stopband wavelength and bandwidth, is essential [24]. ...
We show that both the optical stopband wavelength and effective bandwidth of films of gel-immobilized loosely packed colloidal photonic crystals can be controlled over a wide range. When the gelation reagent of the charge-stabilized colloidal crystals was photopolymerized under ultraviolet light using different upper- and bottom-light intensities, it resulted in a gel-immobilized colloidal crystal film with a broadened Bragg reflection peak. Moreover, the width of the Bragg peak increased from 30 to 190 nm as the difference between the light intensities increased. Films with wider Bragg peaks exhibited a brighter reflection color because of the superposition of the shifted Bragg reflections. Furthermore, the Bragg wavelength could be varied over a wide range (500–650 nm) while maintaining the same broadened effective bandwidth by varying the swelling solvent concentration. These findings will expand the applicability of colloidal crystals for use in photonic devices and color pigments.
... For example, colloidal crystals immobilized in a hydrogel can change the optical stop-band wavelength or Bragg reflection colour through changes in the gel volume corresponding to environmental changes such as temperature, 1,2 pH, 3,4 ionic strength, [5][6][7][8] and solvent. 9,10 These properties are also expected to be applicable in simple sensors and indicators that detect changes in environmental conditions and indicate those through changes in the reflection colour. One of the most intriguing applications of such tunable photonic crystals is a strain sensor. ...
High-quality elastomer-immobilized colloidal crystal films with low particle volume fractions can be prepared using hydrogel-immobilized single-crystalline colloidal crystal films processed by shear flow. The solvent-free elastomer film demonstrated a full-colour change from red to blue with high uniformity over a cm² scale, achieved by varying the mole fraction of monomers in the hydrogel. Owing to the low particle volume fraction, the elastomer film exhibited a colour change from red to blue upon stretching, and the maximum strain reached 120%. The film provided reversible and repeatable colour changes during extension without residual strain. The prepared films have the potential to be used in simple strain sensors to express invisible strains through colour change.
... However, the interaction between these NPs and dispersing solvents and the influence of the solvents on the properties of NPs were mostly neglected. 36,37 Within this context, the swelling behaviors of polymeric NPs in corresponding dispersing solvents need to be systematically investigated. This not only serves to gather deeper comprehension of their dynamic structure and explore proper methods for size control but also allows us to understand the effect of the surface functionalities on the overall behaviors of polysaccharide-derived NPs, which has rarely been studied. ...
Tunable colloidal photonic crystal films consisting of loosely packed colloidal crystals immobilized in elastomers were prepared. The prepared soft film was adhered to an aluminum specimen and the tensile testing was performed. Before applying the tensile force, the film exhibited red color due to Bragg reflection from (111) lattice planes of the face-centered cubic structure, which are parallel to the film surface. With increasing strain on the specimen, the Bragg wavelength of the colloidal crystals was blue-shifted, mainly owing to reduction of the lattice spacing. Consequently, the color of the film changed to orange, yellow, and green in accordance with increasing strain. The prepared films can be used as simple sensors that detect the strain on the materials to which they are adhered based on color change.
Mechanical nondiscoloring and antistretching photonic crystal (PC) films, especially those with stable structure colors during deformation, have great potential applications in wearable display devices, decoration, and packaging. Here, PC films with antistretching and invariant structural colors during deformation were prepared, by combining Zn²⁺ coordinated elastic material and hydroxypropyl methylcellulose (HPMC) with polystyrene@silica (PS@SiO2) colloidal crystals. The PC films release energy by forming local fractures at a microscopic level during the straining process but the lattice spacing and effective refractive index of the local array do not change. According to the Bragg law, the structure color remains unchanged. The introduction of HPMC gave the PC films excellent tensile properties, and the maximum tensile strength reached 10 MPa. And after 100 times of stretching, bending and compression cycles, the structural color remained unchanged.
In this study, a novel flexible and robust dual-network supramolecular elastic film with solvent resistance and brilliant structural colors was prepared by combining a Zn²⁺-crosslinked supramolecular elastic film with polystyrene@silica (PS@SiO2) colloidal crystals. This structurally colored supramolecular elastic material consisted of a covalent support network formed by three different monomers and a Zn²⁺-crosslinked polyacrylic acid (PAA) coordination network, which provided high mechanical strength and flexibility. The tensile and compression stress of this structural color reached 3.26 MPa at a strain of 187% and a pressure of 300 N. The reflectance wavelength of the structural color film remained unchanged after loading–unloading cycles and compression cycles. The structural color film could be bent and unfolded without heating or the application of an external stimulus. Moreover, the structural color film exhibited resistance to solvents in saturated organic vapors and remained color invariant.
