Confined microenvironments in biomacromolecules arising from molecular crowding account for their well‐defined biofunctions and bioactivities. To mimick this, synthetic polymers to form confined structures or microenvironments are of key scientific value, which have received significant attention recently. To create synthetic confined microenvironments, molecular crowding effects and topological cooperative effects have been applied successfully, and the key is balance between self‐association of structural units and self‐repulsion from crowding‐induced steric hindrance. In this article, formation of confined microenvironments from stimuli‐responsive dendronized polymers carrying densely dendritic oligoethylene glycols (OEGs) moieties in their pendants is presented. These wormlike thick macromolecules exhibit characteristic thermoresponsive properties, which can provide constrained microenvironments to encapsulate effectively guest molecules including dyes, proteins, or nucleic acids to prevent their protonation or biodegradation. This efficient shielding effect can also mediate chemical reactions in aqueous phase, and even enhance chirality transferring efficiency. All of these can be switched off simply through the thermally‐induced dehydration and collapse of OEG dendrons due to the amphiphilicity of OEG chains. Furthermore, the switchable encapsulation and release of guests can be greatly enhanced when these dendronized polymers are used as major constituents for fabricating bulk hydrogels or nanogels, which provide a higher‐level confinement.

OEGylated cyclodextrin-threaded polyrotaxanes (PRXs) capped with UV-cleavable stoppers were synthesized, and their thermoresponsive and degradable behavior were investigated. These PRXs in aqueous solutions exhibit fast thermally induced phase transitions and small hysteresis as well as tunable phase transition temperatures, which are quite distinct from previous methylated PRXs. Based on the mechanically interlocked architecture, PRXs are stable in solutions but can be completely degraded into hydrophilic components upon UV cleavage of stoppers. As a consequence, the thermoresponsive behavior of PRXs was switched off. Furthermore, micrometer-scale globular aggregates were formed from thermoresponsive PRXs above their phase transition temperatures but disaggregated quickly upon cooling or UV irradiation. This phenomenon was utilized to take these PRXs as unique carriers for guests with dually controlled release by both temperature and light. The present work provides efficient synthesis of a new class of thermoresponsive interlocked polymers with on-demand degradation, and the findings illustrate the prominent effect of PRX architecture on the remarkable thermoresponsive and degradable behavior.

Synthesis of noble metal nanoparticles with controllable sizes and morphologies by environment-friendly methods is scientifically important and technologically challenging. Here, we report fabrication of monodispersed silver nanoparticles (AgNPs) in aqueous conditions with dendronized chitosan oligosaccharides (CSOs) as templates. These dendronized CSOs carry three-folded dendritic oligoethylene glycol pendants, which integrate the features of biocompatibility from oligosaccharides, as well as multi-valency and crowding structure effects from dendronized topologies. The crowded dendrons afford a hydrophobic microenvironment for these polymers to complex with silver ions and mediate their conversion to form narrowly distributed AgNPs when triggered with low energy visible light. AgNPs embedded within dendronized CSOs formed stable nanocomposites, which exhibit excellent antimicrobial activity against both Gram-positive and Gram-negative bacteria. Characteristic encapsulation and shielding effects, together with their excellent biocompatibility, make these CSOs appealing for eco-friendly and controllable fabrication of precious metal nanoparticles, which are expected to find various bio-applications.

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Fabrication of alloy metal nanoparticles with controllable size, morphology, and different compositions under environmentally benign and sustainable conditions is important for their versatile applications. Here, we report on a route for the visible-light-triggered fabrication of monodispersed gold and silver alloy nanoparticles (Au@AgNPs) in aqueous conditions through the confinement of dendronized chitosans (DCSs). These DCSs carry densely packed threefold dendritic oligoethylene glycol (OEG) pendants, which integrate the features of water solubility and biocompatibility from chitosan, as well as thermoresponsiveness, crowded structures, and multivalency from dendronized topologies. These DCSs provide structure-dependent confined microenvironments on the molecular level to complex with metal ions and mediate their conversion into Au@AgNPs upon irradiation with visible light without any external chemical reducer. Au@AgNPs with different Au and Ag compositions are embedded within the DCSs to form stable nanocomposites, which show promising photothermal properties. In addition, these nanocomposites exhibit excellent catalytic activity in the reduction of 4-nitrophenol.