Development of a Self-Healing Gel with Self-Healing Kinetics That Can Be Controlled by Heat.

A self-healing gel with self-healing kinetics that can be regulated by heat is developed. The gel is composed of a polymer having benzophenone (BP) substituents, which are cross-linked with a main alkyl chain via ester bonds, titanium chloride, and zinc. This gel material shows a self-healing property at room temperature. Also, its self-healing behavior can be accelerated by heating the gel. This gel having self-healing kinetics that can be regulated by heat is favorable for practical use. When we want to use a self-healing property as a stop-gap measure, a rapid self-healing property is demanded. On the other hand, when we want materials repaired beautifully or decomposed surfaces need to be attached beautifully, a slow self-healing property is favorable. These opposite demands can be answered by the gel with self-healing kinetics that can be regulated by heat.

Development of an Adhesive Gel System for Changing the Structure and Properties of Its Adhesive Joint via Reactions with Amine Molecules after Adhesion.

Adhesive gel systems are attracting increasing interest from researchers to use gel materials for artificial biomaterials and engineering materials. Humans, among other living beings, eat foods, get nutrients from them, and use these nutrients to grow up day by day. The shapes and characteristics of their bodies change depending on the nutrients they get. This research develops an adhesive gel system that the chemical structure of the adhesive joint and their properties can be changed and regulated after adhesion, like the growth of living beings. The adhesive joint, which is constructed using a linear polymer comprising a cyclic trithiocarbonate monomer and acrylamide, developed in this research reacts with amines and forms chemical structures depending on amines. The differences in chemical structures endow the adhesive joint with the characteristics and properties that depend on the reaction of amines with the adhesive joint.

Preparation and Permeation Properties of a pH-Responsive Polyacrylic Acid Coated Porous Alumina Membrane.

A pH-responsive membrane is expected to be used for applications such as drug delivery, controlling chemical release, bioprocessing, and water treatment. Polyacrylic acid (PAA) is a pH-responsive polymer that swells at high pH. A tubular α-alumina porous support was coated with PAA by grafting to introduce appropriate functional groups, followed by polymerization with acrylic acid. The permeances of acetic acid, lactic acid, phenol, and caffeine were evaluated by circulating water inside the membrane, measuring the concentration of species that permeated into the water, and analyzing the results with the permeation model. The permeance of all species decreased with increasing pH, and that of phenol was the largest among these species. At high pH, the PAA carboxy group in the membrane dissociated into carboxy ions and protons, causing the swelling of PAA due to electrical repulsion between the negative charges of the PAA chain, which decreased the pore size of the membrane and suppressed permeation. Furthermore, the electrical repulsion between negatively charged species and the PAA membrane also suppressed the permeation. The results of this study demonstrated that the PAA-coated α-alumina porous support functioned as a pH-responsive membrane.

Adhesive Hydrogel System Based on the Intercalation of Anionic Substituents into Layered Double Hydroxides.

Hydrogels comprising anionic substituents in their polymer network were synthesized and adhered to each other following application of layered double hydroxides (LDHs) onto their surfaces. The resulting systems displayed high adhesive strength and tolerance for changes in parameters like solvent, salt concentration, and temperature. In experiments involving hydrogels with bulky anionic substituents, it was confirmed that the efficiency of the intercalation of the anionic groups into the layered inorganic compound LDH determines the strength of the adhesion. Moreover, intercalation-based adhesive joints connecting anionic hydrogels displayed higher tolerance for saline solutions than adhesive joints relying on electrostatic interactions between anionic and cationic hydrogels, even though, because of the electrostatic repulsion between charges with the same sign, one would expect that polymer networks comprising opposite charges would tolerate better the disruption caused by high saline concentration.

Reversing Redox Responsiveness of Hydrogels due to Supramolecular Interactions by Utilizing Double-Network Structures.

Stimuli-responsive hydrogels have been actively researched, and some of them have been put into practical use. When we create and use stimuli-responsive hydrogel materials, controlling stimuli responsiveness of hydrogels is a very important issue. In this research, we prepared hydrogels having single-network (SN) or double-network (DN) gel structures with the host-guest interaction groups cyclodextrin and methyl viologen and evaluated their stimuli responsiveness. The results of the tensile and compression tests showed that the hydrogels with SN and DN structures exhibited opposite stimuli responsiveness in response to the redox reaction of methyl viologen through the association and dissociation of the host molecule, ß-cyclodextrin, and the guest molecule, methyl viologen. Spectroscopic measurements and rheological studies all indicated that this difference in stimuli responsiveness originated from the polymer-network structures. In addition, a chemically cross-linked DN gel was prepared and its redox responsiveness was evaluated.

Highly Tolerant and Durable Adhesion between Hydrogels Utilizing Intercalation of Cationic Substituents into Layered Inorganic Compounds.

Adhering hydrogel systems are important particularly in the medical field because they can be used as adhesives cross-linking between living tissues. In this research, hydrogels including cationic substituents prepared via free-radical polymerization were brought into contact after applying an aqueous dispersion of the layered inorganic compound Micromica to their surfaces. As a result, the hydrogels adhered to each other due to the intercalation of cationic substituents included in the gel networks into the interlayers of Micromica. As the water content ratio of hydrogels decreased, the adhesive strength came to be higher, and finally the adhesively bonded joint supported a tensile load of 10 kg. Moreover, it was confirmed that the adhered hydrogels have high tolerance toward various environments, such as high or low temperatures and solvents.

Linear versus dendritic molecular binders for hydrogel network formation with clay nanosheets: studies with ABA triblock copolyethers carrying guanidinium ion pendants.

ABA-triblock copolyethers 1a-1c as linear polymeric binders, in combination with clay nanosheets (CNSs), afford high-water-content moldable supramolecular hydrogels with excellent mechanical properties by constructing a well-developed crosslinked network in water. The linear binders carry in their terminal A blocks guanidinium ion (Gu(+)) pendants for adhesion to the CNS surface, while their central B block comprises poly(ethylene oxide) (PEO) that serves as a flexible linker for adhered CNSs. Although previously reported dendritic binder 2 requires multistep synthesis and purification, the linear binders can be obtained in sizable quantities from readily available starting materials by controlled polymerization. Together with dendritic reference 2, the modular nature of compounds 1a-1c with different numbers of Gu(+) pendants and PEO linker lengths allowed for investigating how their structural parameters affect the gel network formation and hydrogel properties. The newly obtained hydrogels are mechanically as tough as that with 2, although the hydrogelation takes place more slowly. Irrespective of which binder is used, the supramolecular gel network has a shape memory feature upon drying followed by rewetting, and the gelling water can be freely replaced with ionic liquids and organic fluids, affording novel clay-reinforced iono- and organogels, respectively.

Hierarchical carbon nanotube assemblies created by sugar-boric or boronic acid interactions.

We previously found that polysaccharide "schizophyllan (SPG)" can entrap as-grown and cut single-walled carbon nanotubes (as-SWNTs and c-SWNTs, respectively): we here reported that the c-SWNT-s-SPG (single stranded SPG) composites thus obtained can be aligned regularly using the covalent bond formation between boric acid or boronic acid derivatives and the 4,6-dihydroxyl group of the glucose side-chain unit.

Beta-1,3-glucan polysaccharide (schizophyllan) acting as a one-dimensional host for creating supramolecular dye assemblies.

We have demonstrated that one-dimensional supramolecular dye assemblies with a uniform diameter can be created by utilizing schizophyllan (SPG) as a one-dimensional host. In the supramolecular nanofibers, the dye molecules are assembled into the different aggregation modes depending on the preparation procedures. The findings establish that SPG is useful for creating the supramolecular nanofibers, where temporal superstructures can be stabilized by the SPG-specific helical higher-order structure. [structure: see text].