Enhanced confinements to modulate efficient reversible isomerization of donor-acceptor Stenhouse adducts in water through cooperative crowding in thermoresponsive dendronized nanogels

[Display omitted] •Interchain cooperations in dendronized nanogels modulate hydration of the DASAs.•Thermally dehydrated and collapsed dendritic OEGs provide enhanced crowding effects.•Dendritic crowding confines visible light mediated isomerization of DASAs in water.•Confined isomerization of DASAs in water exhibits excellent fatigue resistance.•Reversible isomerization of the DASAs is demonstrated for information encryption. Nature has provided excellent examples to modulate the reversible photoisomerization in aqueous media, however, to modulate reversible isomerization of hydrophobic dyes in aqueous media remains a great challenge. Here, we report on reversible isomerization of donor–acceptor Stenhouse adducts (DASAs) in water through confinement from dendronized nanogels. These thermoresponsive dendronized nanogels contains three-fold dendritic oligoethylene glycol (OEG) pendants and are prepared through crosslinking polymerization of the corresponding dendritic macromonomer at elevated temperature. Confinement of the nanogels on isomerization of DASAs is dependent both on hydrophilicity of DASAs and nanogel morphologies, narrated by efficient interchain cooperative interactions within the nanogels. To illustrate the interchain cooperative effects on the confinement, a linear dendronized polymer carrying the same dendritic OEGs was prepared and used for comparison. The dendronized nanogels act as “sponges” to efficiently encapsulate the DASAs from the water phase, and simultaneously facilitate them to transfer partially from the hydrophilic cyclic state into the hydrophobic linear state. This isomerization can be greatly enhanced at elevated temperature due to thermal dehydration, collapse-enhanced hydrophobicity and crowded packing of the dendritic OEGs within the nanogels. Reversible isomerization of DASAs within the matrices of the dendronized nanogels was used to demonstrate the principle of information encryption in aqueous media driven by visible light, and a photo-printed QR code could be reversibly written and erased through alternative heating to elevated temperature and photoirradiation with visible light. We therefore believe that the protocol developed in the present work provides a convenient route to confine the physiochemical states of encapsulated guest moieties in water, and is anticipated to create new prospectives in modulating functions and properties of targeted species or molecules through dendritic molecular crowding.