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.

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.

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.

A gradient self-oscillating polymer brush has been designed to achieve controlled unidirectional motion.

We have developed a novel polymer brush surface exhibiting autonomous swelling-deswelling changes driven by the Belousov-Zhabotinsky (BZ) reaction, that is, the self-oscillating polymer brush. In this system, the ruthenium tris(2,2'-bipyridine) [Ru(bpy)] catalyst-conjugated polymer chains are densely packed on the solid substrate. It is expected that the BZ reaction in the polymer brush would be influenced by the immobilization effect of the catalyst. To clarify the effect of the immobilization of the catalyst on the self-oscillating polymer brush, the self-oscillating behavior of the polymer brush was investigated by comparing it with that of other self-oscillating polymer materials, the free polymer, and the gel particle under various initial substrate concentrations. The initial substrate dependency of the oscillating period for the polymer brush was found to be different from those for the free polymer and the gel particle. Furthermore, the oscillatory waveform was analyzed on the basis of the Field-Körös-Noyes model. These investigations revealed that the dense immobilization of the self-oscillating polymer on the surface restricted accessibility for the Ru(bpy) moiety. These findings would be helpful in understanding the reaction-diffusion mechanism in the polymer brush, which is a novel reaction medium for the BZ reaction.

Reversible conversion between planar nanosheets and 3D structures in response to specific triggers would enable construction of nanodevices with useful electronic, optical, mechanical, biological, and surface properties. Here, we describe controlled formation, stabilization, and 2D-3D conversion of noncanonical planer lipid nanosheets. The lipid nanosheets were generated from vesicles by the addition of mixture of amphiphilic peptides and cationic copolymers having peptide-chaperoning activity. By refining the copolymer structure, autonomous and reversible conversion between 2D nanosheets and cell-sized 3D vesicles in response to triggers, such as pH and enzymatic activity, was achieved.We have reported that a cationic graft copolymer with a polycation backbone and water soluble graft chains has chaperone-like activity toward DNA [6] and peptides. [7] Poly(allylamine)-graft-dextran (PAA-g-Dex, Figure 1a) activates membrane-disruptive acidic peptide, E5, by facilitating folding of the peptide into an active amphiphilic helical conformation ( Figure 1b). E5 chaperoned by the copolymer had considerably higher membrane-disruptive activity than that observed for E5 alone. [7] To understand the effect of the copolymer and E5 on lipid membrane, a suspension of fluorescent-labeled vesicles was incubated with E5, PAA-g-Dex having 92 wt% dextran, or their mixture under physiological salt and pH conditions (10 × 10 −3 m HEPES (4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid)-NaOH (pH 7.4), 140 × 10 −3 m NaCl). The addition of E5/PAA-g-Dex caused a change from circles to lines in confocal microscopic images ( Figure 1c,d and Figure S4, Supporting Information), suggesting that the spherical vesicle structure was changed to a sheet structure. 3D image reconstructed from z-stack images also suggested morphological change from vesicle to sheet by E5/PAA-g-Dex ( Figure S5, Supporting Information). From the images, we calculated fraction of nanosheet (number of nanosheets/number of all lipid assemblies × 100). Most vesicles (92%, n > 300) were converted to the sheet structure within 5 min of E5/PAA-g-Dex addition. Previously, mesoscale nanosheet structures were observed by the addition of proteins having FERM domain, [8] which are cytoskeletal proteins, to lipid vesicles. However, the efficiency of conversion to the nanosheet structure induced by the proteins Nanosheets have thicknesses on the order of nanometers and planar dimensions in the micrometer range. Nanomaterials that are capable of converting reversibly between 2D nanosheets and 3D structures in response to specific triggers can enable construction of nanodevices. Supra-molecular lipid nanosheets and their triggered conversions to 3D structures including vesicles and cups are reported. They are produced from lipid vesicles upon addition of amphiphilic peptides and cationic copolymers that act as peptide chaperones. By regulation of the chaperoning activity of the copolymer, 2D to 3D conversions are reversibly triggered, allowing tuning of lipid bilayer structures an...

A surface-grafted hydrogel was successfully synthesized by immobilization of the ATRP initiator at the surface region of the gel and the subsequent ARGET ATRP step. This is the first example of a bulk hydrogel with a dense surface-localized layer of a grafted polymer and "active" permeation control of the gel.

Herein, we describe the physicochemical aspects of the Belousov-Zhabotinsky (BZ) reaction in hydrated protic ionic liquids (PILs) combined with different cations with a hydrogen sulfate ([HSO]) anion. PILs were prepared from the neutralization reactions of sulfuric acid with 13 different aliphatic amines. The amine structure was selected to investigate the effect of the number of active protons, alkyl chain length (hydrophilicity), and cationic linearity on the mechanism of the BZ reaction. The pK values of PILs were significantly higher (pK = 1.0-2.5) than those of inorganic acids (HSO = -3.0; HNO = -1.4), the conventional proton source in a BZ reaction. A periodic redox oscillation was observed in Ru(bpy) when appropriate amounts of BZ reaction substrates (NaBrO oxidant; malonic acid reductant) were added to the hydrated PILs. A long-lasting BZ oscillation was realized when hydrophilic cations (ammonium, ethylammonium, and dimethylethylammonium) were employed. Interestingly, a large ΔA (oscillation amplitude of absorbance for the scale of the oscillation stability observed after 5000 s from the initiation of the BZ reaction) was achieved for PILs possessing less than four carbon atoms in their cationic structure. The apparent BZ oscillation activation energy (E) in the hydrated PILs was estimated to be ∼40 kJ mol, which is 30 kJ mol less than that observed in a conventional system. The catalytic reaction in the BZ reaction subprocess suppresses the total activation energy of the reaction. To realize long-lasting self-oscillating polymeric materials acting under milder condition, we demonstrated an autonomous coil-globule polymer chain transition (BZ-driven) that directly converts chemical energy to mechanical motion in hydrated PILs without freely diffusing Ru(bpy) metal catalyst. Ethylammonium hydrogen sulfate ([ea-H][HSO]) is selected as the suitable proton source for the BZ reaction. A well-defined self-oscillating polymer that incorporated Ru(bpy) metal catalyst into the polymer backbone accompanied by good compatibility in hydrated [ea-H][HSO] is successfully prepared by ATRP, followed by postmodification of the metal catalyst. The rhythmic solubility changes of the polymer under milder conditions, realized by combination with PILs, will expand the potential applications of PILs to novel functional materials.