Mixed Copolymer Adlayers Allowing Reversible Thermal Control of Single Cell Aspect Ratio

Thermoresponsive Lamellar Hydrogels with Tunable Turbidity, Structural Color, and Anisotropic Swelling

We report a thermoresponsive anisotropic photonic hydrogel: poly(dodecyl glyceryl itaconate)/polyacrylamide-poly(N-isopropylacrylamide) hydrogel (PDGI/PAAm-PNIPAM hydrogel). Hydrogels with uniaxially aligned lamellar bilayers possess bright structural color and swelling anisotropy, while PNIPAM-based hydrogels exhibit distinct thermoresponsive properties around a lower critical solution temperature (LCST). Hybridization of thermoresponsive PNIPAM with the lamellar hydrogel can give the anisotropic photonic hydrogel various fascinating thermoresponsive properties, such as structural color/turbid transition, thermoresponsive structural color, and anisotropic deswelling/reswelling behavior by temperature stimuli. The temperature-induced changes in turbidity, structural color, and anisotropic swelling of the gel around the LCST can be tuned by controlling the incorporated PNIPAM density. PNIPAM can be regioselectively incorporated into the specific region of the lamellar hydrogels by photomasking during UV polymerization. The PDGI/PAAm-PNIPAM hydrogel can find diverse promising applications such as smart windows and smart displays.

Thermoresponsive Fluorescence Switches Based on Au@pNIPAM Nanoparticles

Despite numerous studies emphasizing the plasmonic impact on fluorescence, the design of a dynamic system allowing on-demand fluorescence switching in a single nanostructure remains challenging. The reversibility of fluorescence switching and the versatility of the approach, in particular its compatibility with a wide range of nanoparticles and fluorophores, are among the main experimental difficulties. In this work, we achieve reversible fluorescence switching by coupling metal nanoparticles with fluorophores through stimuli-responsive organic linkers. As a proof of concept, we link gold nanoparticles with fluorescein through thermoresponsive poly(N-isopropylacrylamide) at a tunable grafting density and characterize their size and optical response by dynamic light scattering, absorption, and fluorescence spectroscopies. We show that the fluorescence emission of these hybrid nanostructures can be switched on-demand using the thermoresponsive properties of poly(N-isopropylacrylamide). The described system presents a general strategy for the design of nanointerfaces, exhibiting reversible fluorescence switching via external control of metal nanoparticle/fluorophore distance.