Responsive Block Copolymer Photonic Microspheres

Responsive photonic crystals (PCs) have attracted much attention due to their broad applications in the field of chemical and physical sensing through varying optical properties when exposed to external stimuli. In particular, assembly of block copolymers (BCPs) has proven to be a robust platform for constructing PCs in the form of films or bulk. Here, the generation of BCPs photonic microspheres is presented with 3D periodical concentric lamellar structures through confined self‐assembly. The structural color of the spherical PCs can be tuned by selective swelling of one block, yielding large change of optical property through varying both layer thickness and refraction index of the domains. The as‐formed spherical PCs demonstrate large reflection wavelength shift (≈400–700 nm) under organic solvent permeation and pH adjustment. Spherical shape and structural symmetry endow the formed spherical PCs with rotation independence and monochrome, which is potentially useful in the fields of displays, sensing, and diagnostics.     

Colloid‐in‐Liquid Crystal Gels that Respond to Biomolecular Interactions

This paper advances the design of stimuli‐responsive materials based on colloidal particles dispersed in liquid crystals (LCs). Specifically, thin films of colloid‐in‐liquid crystal (CLC) gels undergo easily visualized ordering transitions in response to reversible and irreversible (enzymatic) biomolecular interactions occurring at the aqueous interfaces of the gels. In particular, LC ordering transitions can propagate across the entire thickness of the gels. However, confinement of the LC to small domains with lateral sizes of ～10 μm does change the nature of the anchoring transitions, as compared to films of pure LC, due to the effects of confinement on the elastic energy stored in the LC. The effects of confinement are also observed to cause the response of individual domains of the LC within the CLC gel to vary significantly from one to another, indicating that manipulation of LC domain size and shape can provide the basis of a general and facile method to tune the response of these LC‐based physical gels to interfacial phenomena. Overall, the results presented in this paper establish that CLC gels offer a promising approach to the preparation of self‐supporting, LC‐based stimuli‐responsive materials.     

Tunable Photonic Microspheres of Comb‐Like Supramolecules

Photonic crystals (PCs) are ideal candidates for reflective color pigments with high color purity and brightness due to tunable optical stop band. Herein, the generation of PC microspheres through 3D confined supramolecular assembly of block copolymers (polystyrene‐block‐poly(2‐vinylpyridine), PS‐b‐P2VP) and small molecules (3‐n‐pentadecylphenol, PDP) in emulsion droplets is demonstrated. The intrinsic structural colors of the PC microspheres are effectively regulated by tuning hydrogen‐bonding interaction between P2VP blocks and PDP, where reflected color can be readily tuned across the whole visible spectrum range. Also, the effects of both PDP and homopolymer (hPS) on periodic structure and optical properties of the microspheres are investigated. Moreover, the spectral results of finite element method (FEM) simulation agree well with the variation of structural colors by tuning the periodicity in PC microspheres. The supramolecular microspheres with tunable intrinsic structural color can be potentially useful in the various practical applications including display, anti‐counterfeit printing and painting.     

聚合物凝胶光子晶体及其对物理环境的响应

文中简要介绍了物理响应性光子晶体的国内外研究动态。重点介绍以下几种物理响应性光子晶体:温度响应性光子晶体,溶剂响应性光子晶体,电场响应性光子晶体,磁场响应性光子晶体,机械力响应性光子晶体等。     

Light‐Patterned Crystallographic Direction of a Self‐Organized 3D Soft Photonic Crystal

Uniform and patterned orientation of a crystallographic direction of ordered materials is of fundamental significance and of great interest for electronic and photonic applications. However, such orientation control is generally complicated and challenging with regard to inorganic and organic crystalline materials due to the occurrence of uncontrollable dislocations or defects. Achieving uniform lattice orientation in frustrated liquid‐crystalline phases, like cubic blue phases, is a formidable task. Taming and tailoring the ordering of such soft, cubic lattices along predetermined or desired directions, and even imparting a prescribed pattern on lattice orientation, are more challenging, due to the entropy‐domination attribute of soft matter. Herein, we disclose a facile way to realize designed micropatterning of a crystallographic direction of a soft, cubic liquid‐crystal superstructure, exhibiting an alternate uniform and random orientation of the lattice crystallographic direction enabled by a photoalignment technique. Because of the rewritable trait of the photoalignment film, the pattern can be erased and rewritten on‐demand by light. Such an oriented soft lattice sensitively responds to various external stimuli such as temperature, electric field, and light irradiation. Furthermore, advanced reflective photonic applications are achieved based on the patterned crystallographic orientation of the cubic blue phase, soft lattice.     

Photonic Devices Out of Equilibrium: Transient Memory,Signal Propagation,and Sensing

Soft photonic materials are important for sensors, displays, or energy management and have become switchable under static equilibrium conditions by integration of responsive polymer features. The next step is to equip such materials with the ability for autonomously dynamic and self‐regulating behavior, which would advance their functionality and application possibilities to new levels. Here, this study shows the system integration of a nonlinear, biocatalytic pH‐feedback system with a pH‐responsive block copolymer photonic gel, and demonstrates autonomous transient memories, remotely controlled signal propagation, and sensing. This study utilizes an enzymatic switch to program the lifetime of the reflective state of a photonic gel, and induces propagation of pH‐waves extinguishable by illumination with UV‐light. The described combination of nonlinear chemistry and responsive photonic gels opens pathways toward out‐of‐equilibrium photonic devices with active and autonomous behavior useful for sensing, computation, and communication.     

pH响应性光子晶体

响应性光子晶体(Responsive photonic crystals,RPCs)具有无毒、无标记、低消耗和裸眼可视的优点,pH响应性光子晶体(pH-RPCs)为食品安全、生物医药、水体环境等领域提供了一种简便的检测方式。目前主要发展了胶体粒子组装体/反蛋白石、层状堆叠和全息三种结构类型的pH-RPCs。本文在介绍光子晶体(Photonic crystals,PCs)pH响应原理的基础上,从制备方法、结构特点和pH响应性能(如灵敏度、响应时间、可视化)等方面对上述pH-RPCs进行了详细的综述,分析总结了它们各自的优势和不足,并对其未来的发展进行了展望。