Multiresponsive Polymer Nanocomposite Liquid Crystals Having Heterogeneous Phase Transitions for Battery-Free Temperature Maintenance Indicators.

Multiresponsive functional materials that respond to more than one external stimulus are promising for novel photonic, electronic, and biomedical applications. However, the design or synthesis of new multiresponsive materials is challenging. Here, this work reports a facile method to prepare a multiresponsive colloidal material by mixing a liquid-crystalline 2D nanocolloid and a functional polymer colloid. For this purpose, electrically sensitive exfoliated α-ZrP 2D nanocolloids and thermosensitive block copolymer colloids that are dispersed well in water are mixed. In the liquid-crystalline nanocomposite, nematic, antinematic, or isotropic assemblies of α-ZrP, nanoparticles can be electrically and selectively obtained by applying electric fields with different frequencies; furthermore, their rheology is thermally and reversibly controlled through thesol-gel-sol transition. The nanocomposite exhibits a solid gel phase within a predesigned gel temperature range and a liquid sol phase outside this range. These properties facilitate the design of a simple display device in which information can be electrically written and thermally stabilized or erased, and using the device, a battery-free temperature maintenance indication function is demonstrated. The proposed polymer nanocomposite method can enrich the physical properties of 2D nanocolloidal liquid crystals and create new opportunities for eco-friendly, reusable, battery-free electro-optical devices.

Optical devices constructed from multiresponsive microgels.

Novel multiresponsive microgels based on poly(N-isopropylacrylamide) were synthesized to contain triphenylmethane leucohydroxide, and used to construct etalons. The optical properties of the resultant etalons were investigated, and their response to ultraviolet and visible irradiation, solution pH changes, and the presence of a mimic of the nerve agent Tabun characterized. We clearly show that the optical properties of the device depended dramatically on these stimuli. This investigation illustrates the versatility of the microgel-based etalon structure, and showcases the clear utility of such devices for remote actuation, color tunable optics, sensing, and potential remotely triggered drug delivery applications.

2-Ureido-4-pyrimidone-based hydrogels with multiple responses.

Functionalisation of poly[2-(dimethylamino)ethyl methacrylate] (a responsive methacrylate) with light-activatable 2-ureido-4-pyrimidone units allows a supramolecular hydrogel to be obtained that combines temperature, light and pH response with self-healing properties. Whereas the self-healing properties of this system were described previously, this report focuses on its response to different external stimuli, which is studied by quartz crystal microbalance analysis of thin films of the material. Reversible collapse with increasing temperature, reversible swelling with decreasing pH and irreversible shrinkage with UV exposure are demonstrated. These three stimuli are combined to have externally gated or tuned responses. Thermo-induced swelling and shrinkage can be reversibly inhibited by changing the pH and irreversibly regulated by exposure to light of different doses. These materials represent the first general strategy to obtain responsive self-healing hydrogels in which the response and the self-healing properties are decoupled from each other and can be tuned independently.