Polystyrene@poly(methyl methacrylate-butyl acrylate) Core–Shell Nanoparticles for Fabricating Multifunctional Photonic Crystal Films as Mechanochromic and Solvatochromic Sensors

Abstract

Responsive photonic crystals (PCs) with a nanoscale band gap assembled by colloidal nanospheres have been increasingly utilized in detection and sensing devices owing to their attractive ability to change color in response to external conditions. However, most of the reported works have been dedicated to single-functional PCs, which can only be used as sensors or detectors in a specific situation. Thus, producing a multi-functional PC for various industrial applications remains a challenge. In this work, multi-functional soft PC films (SPCFs) with a brilliant structural color and a robust structure are fabricated by using polystyrene@poly­(methyl methacrylate-butyl acrylate) [PS@P­(MMA-BA)] nanospheres with size in the range of 200–350 nm as building blocks. The SPCFs possess both the mechanochromic and solvatochromic properties owing to the adjustable photonic band gap under stress and polar solvent conditions. The mechanochromic effect of the SPCF under stretching results in a blue shift of the structural color due to the decrease in lattice spacing. In contrast, the solvatochromic mechanism of the SPCF is that it can be swollen by polar solvents, resulting in the increase in the lattice spacing of PCs and a red shift of the structural color. Meanwhile, the SPCF can keep its original structural color while stretched for 20 cycles or when the organic solvent is completely evaporated. Therefore, robust multi-functional SPCFs fabricated by the self-assembly of PS@P­(MMA-BA) nanospheres under gravity sedimentation can respond to stress and organic solvents, showing great potential for use in sensors and detectors.

Photonic Crystal Films Based on Polymer Particles with a Core/Shell Structure Responding to Ethanol

“…In addition, it is obvious that the sensitivity of the resulting photonic crystal films to a low concentration of ethanol vapor (less than 10 vol %) is affected by the composition of the polymer shell . For example, Wang et al described the color change of ordered films based on PSt@poly­(MMA-BA) particles in the presence of not less than 30% ethanol solution. It is worth noting that in ref the PSt@poly­(MMA-BA) particle shell was formed in the presence of allyl methacrylate as a crosslinking agent.…”

Color‐Tuning Mechanism of Electrically Stretchable Photonic Organogels

“…The refractive indexes of the organogel components were considered as n 1 = 1.479 for the elastic organic gel (volume fraction V 1 = 0.26), and n 2 = 1.59 for the rigid nano-scale PS beads (volume fraction V 2 = 0.74). Since the closely packed PS beads were isotropically swollen by the organogel, [83][84][85] V 1 and V 2 could be changed to V 1 ' and V 2 '. The lattice volume between the d 001 spaces became larger due to ultraviolet irradiation increasing the stiffness of the organogel.…”

“…Since the closely packed PS beads were isotropically swollen by the organogel, [ 83–85 ] V 1 and V 2 could be changed to V 1 ’ and V 2 ’. The lattice volume between the d 001 spaces became larger due to ultraviolet irradiation increasing the stiffness of the organogel.…”

A Flexible and Robust Structural Color Film Obtained by Assembly of Surface-Modified Melanin Particles

“…Structural color films have been used in a wide range of applications such as smart displays [51] and strain sensors [52,53] due to their unique coloring properties. The present method can impart an arbitrary polymer layer on the surface of melanin particles, and the resulting particles would be applicable to the fabrication of structural color films with functions such as temperature response [54], mechanochromic [55], and fluorescent properties [56]. Most of these reported materials are prepared by multi-component systems in which light-absorbing materials such as carbon black are added to improve the visibility of the structural color.…”