Yuechuan Wang

Structurally colored materials that change color upon mechanical stimuli have broad potential in stress sensors, wearable devices, and artificial skin. Such materials are conventionally prepared through the self-assembly of colloidal nanoparticles or block copolymers, a process that often involves time-consuming synthesis and purification as well as color inhomogeneity. To enable a simple and scalable route to mechanochromic materials, we employ holographic photopolymerization to fabricate monolithic, structurally colored elastomers. High reflectance and elasticity are achieved by adjusting the matrix formulation, the concentrations of recording monomers and acrylate cross-linker, the film thickness, and the exposure dose. The resulting materials exhibit a relative reflectance above 90% and a reversible mechanochromic shift of approximately 70 nm under 20% tensile strain. This work offers a practical approach to developing mechanically responsive photonic materials for sensing and anticounterfeiting applications.

Structural colouration arises from the interaction of light with nanoscale structures and offers sustainable alternatives to pigment-based colours. However, current structural colour patterning methods rely on multi-step lithographic processes or multiple ink formulations, limiting scalability and spatial resolution. Inspired by melanosome self-assembly in bird feathers, we develop a one-step, mask-free strategy to generate high-resolution structural colour patterns via tunable nanoparticle segregation. During photocuring, silica nanoparticles dispersed in acrylic resin migrate toward oxygen-permeable substrates, forming a nanoparticle-enriched disordered layer. Such segregation is driven by interfacial oxygen inhibition and kinetically governed by the photocuring rate. Using grayscale digital light processing printing, we programmably control the local segregation thickness to create high-resolution structural colour patterns for visual display and information encryption. The segregation structure also affects mid-infrared reflectivity, allowing for infrared camouflage. This scalable approach establishes a mechanistically guided route to multifunctional photonic materials.

Cycloaliphatic diepoxides, CAEs, are well known for their better thermal, chemical and optical properties, compared with the glycidyl ether type epoxides. However, the shortages including low moisture resistance, and high reflective index or high dielectric constant limit their use for the emerging advanced optical and electronic applications, In this work, we have synthesized two new cycloaliphatic diepoxides containing different fluorinated linkers (2,2′‐((2,2,3,3‐tetrafluorobutane‐1,4‐diyl)bis(oxy))bis(7‐oxabicyclo[4.1.0]heptane) (TCE) and 2,2′‐((2,2,3,3,4,4,5,5‐octafluorohexane‐1,6‐diyl)bis(oxy))bis(7‐oxabicyclo[4.1.0]heptane) (OCE) and characterized their chemical structures using ¹H NMR, ¹⁹F NMR, and Fourier transform infrared spectroscopy. We have cured these two fluorine‐containing CAEs, using hexahydro‐4‐methylphthalic anhydride (HMPA) and compared them with a commercial CAE, 3,4‐epoxycyclohexylmethyl‐3,4‐epoxycyclohexanecarboxylate (ERL‐4221) under the same condition. Compared to the cured ERL‐4221 (C‐ERL‐4221), the cured fluorinated CAEs (C‐OCE, C‐TCE) have much better water resistances (saturated water absorption after 6 days in water: 0.70%, 1.72%, and 2.83%, for C‐OCE, C‐TCE, and C‐ERL‐4221, respectively) and lower dielectric constant (D_k) (D_k: 2.54–2.44 and 2.78–2.66 vs. 4.01–4.00 @ 1 Hz‐5 MHz), and similar thermal stability (the statistical heat‐resistant index [T_s]: 169°C, 175°C vs. 175.5°C), although their glass transition temperature (T_g) and storage moduli are lower (T_g: 136°C, 171°C vs. 250°C; moduli: 0.56GPa, 1.25GPa vs. 1.38GPa). These results reveal that fluorine atoms on the linkers effectively reduce dielectric constant and improve hydrophobicity and wettability, providing new insights into the design of fluorine‐containing cycloaliphatic diepoxides.

Demand for electronic materials with improved dielectric properties are increasing. One of the ways to reduce the dielectric constant is to incorporate fluorine atoms. In this article, a novel fluorinated epoxy resin (diglycidol ether of 2,4‐bis (1,1,1,3,3,3‐hexafluoroisopropyl) fluorobenzene (FB‐EP)) with 45.7 wt% fluorine content was synthesized from fluorobenzene, epichlorohydrin and hexafluoroacetone. The structures of desired monomers were characterized by NMR and FTIR. The epoxy resin FB‐EP was cured by copolymerization with hexahydrophthalic anhydride (HHPA) and by homopolymerization catalyzed with boron trifluoride ethylamine (BF₃MEA), respectively. The curing reaction kinetics of the fluorinated epoxy and the properties of the cured materials were studied in comparison with those of common diglycidol ether epoxy resin (BADGE). The results of curing activation energy indicate that FB‐EP is reactive as the BADGE, and the four‐trifluoromethyl groups on FB‐EP do not negatively affect the cationic polymerization reactivity of the epoxy groups. The cured FB‐EP materials had lower moisture absorption, and especially lower dielectric constant (D_k, 2.23) and lower dielectric loss (D_f, 0.011) in the frequency range of 8.2–12.4 GHz. This article provides a base for further study of fluorinated epoxy resin as advanced electronic materials.