An autonomous functional surface has been designed by using self-oscillating polymers that convert the chemical energy of the Belousov-Zhabotinsky reaction into conformational changes of the polymer chains (see picture: red: hydrophobic/collapsed, green: hydrophilic/extended). Self-oscillating polymer brushes were grafted onto the inner surface of a glass capillary, and autonomous propagation of a chemical wave was observed.

As novel functional materials, we developed self-oscillating polymeric materials composed of synthetic polymers coupled with an oscillating chemical reaction, the so-called Belousov–Zhabotinsky (BZ) reaction.

We have developed a novel "self-oscillating" gel that exhibits an autonomous mechanical oscillation without any external stimuli. Here the ternary self-oscillating polymer composed of N-isopropylacrylamide and N-(3-aminopropyl)methacrylamide and Ru(bpy) 3 10 was newly synthesized by atom transfer radical polymerization (ATRP) and the gel was prepared. For the self-oscillating polymers and gels with various compositions, their phase transition and self-oscillating behaviors were investigated considering the potential for biomedical application. It was demonstrated that the swelling-deswelling behavior of the self-oscillating gels can be controlled by changing the composition ratio of the free 15 amino group present in the polymer and the conjugated Ru(bpy) 3 moieties. Therefore the hydrophilic/hydrophobic balance is controllable and adjustable by this composition ratio.

Cells sense and respond not only to biochemical signals but also to biophysical signals (e.g., matrix elasticity). In addition to matrix elasticity, recent studies have revealed that viscoelasticity (e.g., stress relaxation) significantly affects cellular functions, such as spreading, proliferation, and differentiation. Herein, we describe a cytocompatible and dynamic hydrogel that is comprised of well-defined ABA triblock copolymers, which enable significant changes of viscoelastic properties solely by UV light irradiation. The A block contains N-isopropylacrylamide and an acrylate monomer with a coumarin side chain, whereas the B block is biocompatible poly(ethylene oxide). The triblock copolymer forms a physically cross-linked hydrogel under physiologically relevant conditions. However, under UV light irradiation, the viscoelasticity of the hydrogel is dynamically modulated due to the photodimerization of coumarin moieties. After UV illumination, rheological properties of the hydrogel are drastically different, indicating the formation of chemical cross-linking points in the hydrogel. Finally, we demonstrate that the dynamic change in the viscoelasticity of the hydrogel has a significant influence on the behavior of encapsulated cells.

A polymer brush surface with autonomous function has been designed by using a self-oscillating polymer that we developed. The self-oscillation is induced by chemomechanical energy conversion from an oscillating chemical reaction (the Belousov−Zhabotinsky (BZ) reaction) to conformational changes of polymer chains. In this study, the surface nanostructure of polymer brushes were regulated and the spatiotemporal behaviors of self-oscillation were investigated. The target polymer brush surfaces were prepared through surface-initiated atom transfer radical polymerization (SI-ATRP) of N-isopropylacrylamide (NIPAAm) and N-(3aminopropyl) methacrylamide (NAPMAm), and the subsequent conjugation of Ru(bpy) 3 to the amino group of NAPMAm. The characterization of the prepared polymer brush and the free polymer was determined by X-ray photoelectron spectroscopy, atomic force microscopy, attenuated total reflection Fourier transform infrared spectroscopy, UV−vis spectrophotometry, gel permeation chromatography, and 1 H NMR. Their dynamic properties were estimated by quartz crystal microbalance with dissipation and fluorescence microscopy. The amounts of Ru(bpy) 3 immobilized to polymer brush surfaces could be controlled by adjusting the reaction conditions of SI-ATRP and conjugating Ru(bpy) 3 . Importantly, an appropriate structure of polymer brush to give stable oscillation has been indicated from image analysis of chemical wave propagation. Further, several physicochemical parameters to control the oscillating behaviors, including the rate constant of the autocatalytic reaction, the diffusion constant of the activator, and the activation energies for the reaction and diffusion, have been obtained from theoretical consideration. These results will be helpful for developing subsequent applications such as autonomous transport systems.