Polymeric soft materials with molecular recognition: from static binding to dynamic functions in gels, particles, and interfaces.

Molecular recognition governs important chemical events in biology from enzyme catalysis to immune defense and cellular signal transduction, where specificity is expressed not only as affinity but also as regulated, state-dependent function. Translating these principles into synthetic materials and systems has stimulated the development of polymeric soft materials in which binding events are coupled to macroscopic responses. This review focuses on polymeric soft materials such as hydrogels, particles, and interfaces that integrate recognition moieties, including noncovalent and host-guest interactions, biomolecular ligands, and molecularly imprinted cavities, and describes coupling mechanisms that convert binding into macroscopic structural change, transport regulation, and device-readable signals. In macroscopic stimuli-responsive hydrogels, molecular recognition can induce changes in effective crosslink density, hydration, and chain conformation, thereby enabling autonomous gating and representative concepts for glucose-responsive insulin delivery. Miniaturization to particles and micro/nanogels increases accessible surface area and shortens diffusion paths, which often accelerates response kinetics and enhances targeted therapeutics and controlled drug release. At polymer interfaces, especially membranes, thin films, and layers, molecular recognition must be designed together with transport pathways. Antifouling architectures, including zwitterionic polymers, are also important for maintaining selectivity in surface-sensitive measurements such as surface plasmon resonance (SPR). Across these platforms, practical performance is frequently governed not by binding affinity alone but by transport accessibility, layer thickness, and baseline stability against nonspecific adsorption and signal drift. Focusing on the relationships between structures and functions, this review summarizes current progress and outlines design strategies for smart polymer materials that translate molecular binding into functional outputs.