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Production of anisotropic hydrogels that show a direction-dependent structure and properties, which have attracted attention in bio-mimicking, tissue engineering and bio-separation.

Chitosan (CS), an amino-polysaccharide, has applications in various areas, particularly in drinking water and wastewater treatment, with highly efficient properties for binding metal ions. Monoliths have been developed continuously for several decades, and today they hold an impressively strong position in highly efficient separation, ion exchange, catalysis, and chromatography. In our previous study, hierarchical chitin (CT) monolith was fabricated using chemically modified CT through the thermally induced phase separation (TIPS) method. This report generated highly effective, stable, and reusable CS monoliths by deacetylation of CT monoliths. The acquired monoliths demonstrated efficient removal of metal ions from the aqueous solution in a flow system. In order to gain durability in acidic and basic environments, epichlorohydrin (ECH) was used as a crosslinking agent. The crosslinked monoliths exhibited excellent performance in the adsorption of Cu(II) ions from the solution, and good reusability in multiple adsorption-desorption cycles without losing significant performance. The fabricated CS monolith can be modified and applied to various fields such as protein separation, catalyst, and drug delivery.

Poly(phenylene sulfide) (PPS), a high-performance engineering plastic, possesses many desirable characteristics, such as outstanding high-temperature stability, inherent flame resistance, and excellent mechanical properties. Owing to its excellent chemical resistance, the modification of PPS for further applications, such as printed circuit boards (PCBs), is difficult. In this study, a photoinitiated chlorine dioxide radical (ClO2•) was utilized as an oxidant to modify the PPS film surface to improve its hydrophilicity and adhesion properties with different metals. IR and XPS analyses confirmed that oxygen-containing groups are introduced onto the PPS film surface, and its hydrophilicity is improved. Electroless plating was performed to deposit Cu and Ni metals onto the PPS surface, and the strength of adhesion between the polymer and metals was evaluated using a tape test. This novel modification method can be successfully utilized as a pretreatment for electroless plating, showing great potential for application in flexible printed circuits and the automotive industry in the future. Surface oxidation method using chlorine dioxide radical (ClO2•) for poly(phenylene sulfide) (PPS) was developed. During the oxidation reaction, sulfonyl groups and sulfite groups were successfully introduced to the surface of the PPS films. The water contact angle of the surface of the PPS film decreased dramatically after the oxidation, indicating that the surface hydrophilicity was improved. Electroless plating demonstrates that typical metals could be tightly deposited on the surface of oxidized PPS film and cannot be removed. This method provides an effective, clean, energy-saving treatment for super engineering plastics.

The applicability of chitin-based carbon as a supercapacitor electrode material was investigated by adjusting its pore structure through polystyrene latex templating, without significant N doping. 2,2,6,6-tetramethylpiperidinyloxy (TEMPO)-oxidized chitin nanofibers were mixed with polystyrene latex, hydrothermally treated at 220 °C, carbonized, and activated using KOH at 800 °C, yielding activated hierarchical porous carbon. The variation of both polystyrene latex amount and carbonization temperature resulted in changes in the surface area and pore structure, which dictated the degree of pore uniformity and activation efficiency. The pore structure affected activation by allowing the selective removal of amorphous carbon, exposing the basal plane carbon, resulting in higher specific capacitance. By making activated hierarchical porous carbon more conducive to activation, specific capacitance of 567 F g

A polyethylenimine-grafted cellulose monolith was developed for efficient bacterial capture in a continuous flow system. The amino-functionalized monolith showed superior capture capacity for high concentration of both gram-negative (Escherichia coli) and gram-positive (Bacillus subtilis) bacteria compared with the unmodified one. The efficiency and structural stability of the monolith were consistent during bacterial filtering at a high flow velocity. Bacteria were observed to be anchored to the skeleton surface of the monolith. The performance was attributed to the well-interconnected porous structure and strong electrostatic interaction with cells, which endowed the large surface area with retention force allowing for the local adhesion of bacteria in a flow process.

In the present study, we report a simple and eco-friendly method for the synthesis and immobilization of silver nanoparticles (AgNPs) onto functional films using green tea extract as a reducing and capping agent. The freestanding flexible immobilized AgNPs composite was obtained from a 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-mediated tea cellulose (TTC) process. Scanning electron microscopy analysis revealed the homogeneous coating of the AgNPs on the surface of the TTC nanofibers. Ag-TTC-poly(vinyl alcohol) (PVA) composite film was prepared through a simple solvent casting method, which displayed higher antioxidant activity than the TTC-PVA film, and the rate of release of Ag was reduced owing to the immobilized AgNPs. The photocatalytic performance of Ag-TTC-PVA composite film was evaluated along with the investigations of the optical transparency, morphology, and thermal properties. Ag-TTC-PVA composite film showed enhanced photocatalytic property than TTC-PVA film. This study presents a simple approach for the green synthesis of materials with controlled leakage based on Ag-TTC-PVA composite film, which has good potential application prospects in the development for the photocatalytic degradation of certain toxic dyes, thereby paving the way for waste treatment.

In this work, nanocomposites of poly(methyl methacrylate) (PMMA) with cellulose nanofiber (CNF) were prepared by a solution casting technique. CNF was modified by propionic anhydride (PA) to form surface-propionylated CNF (CNFp) to improve its compatibility with the PMMA matrix. CNF, CNFp, and acetylated CNF were compared with respect to their influence as fillers in PMMA composite films by ultraviolet-visible transmittance, haze values, tensile strength testing, and water contact angle measurement. It was demonstrated that 1 wt % of CNFp has good compatibility and uniform dispersion in the PMMA matrix, as demonstrated by the formation of a smooth surface composite film with good transparency, enhanced tensile properties, improved toughness, and lower wettability. Therefore, PMMA/CNFp composite films have great potential for use in several applications such as lightweight transparent materials, window substitutes, and see-through packaging.

Functional materials that can recognize the tumor microenvironment, characterized by acidic or reducing conditions, are needed for the designing of drug delivery carriers for cancer treatment. Hydrogels are potential protein drug carriers because they contain a large amount of water and stimuli-responsive functions can easily be introduced in them. However, it is difficult to introduce multi-stimuli-responsive functions and degradability at the same time. Here, we synthesized thermo- and pH-responsive hydrogels via a coupling reaction between poly(ethylene glycol) diglycidyl ether (PEGDE) and cystamine (CA). The prepared hydrogels showed lower critical solution temperature-type thermoresponsive behavior and pH-responsive swelling changes due to the protonation of secondary and/or tertiary amino groups arising from the crosslinking agent CA. Under reducing conditions, the hydrogels were degraded via the thiol exchange reaction in the presence of dithiothreitol or glutathione. The loading and release properties of FITC-labeled model proteins from the hydrogels were investigated. The loaded amount of the protein increased with decreasing molecular weight or hydrodynamic radius, which is based on the size of the network structure of the hydrogels. Notably, loaded proteins in the hydrogels were released only under reducing conditions, which mimic the tumor microenvironment. Thus, the prepared multi-responsive degradable hydrogels are expected to be used as functional drug delivery carriers for cancer treatment.

We demonstrate liquid-liquid phase separation involving both coacervation and coil-to-globule phase transition of a thermoresponsive polymer. By focusing a near-infrared laser beam into an aqueous solution of poly(N-isopropylacrylamide) (PNIPAM), a single phase-separated polymer microdroplet can be formed and stably trapped at the focal point. Such droplet formation is induced by a local elevation in temperature (induced by a photothermal effect) and an optical force. The technique allows us to selectively analyze a single polymer droplet trapped at the focal point. In this study, we applied this technique to poly(N,N-diethylacrylamide) (PDEA) in water and generated a double-layered PDEA droplet. Such an inhomogeneous and complex microstructure has not been previously observed both in steady-state heating of a PDEA solution and in the PNIPAM system. Moreover, we used micro-Raman spectroscopy to clarify that PDEA underwent dehydration due to a coil-to-globule phase transition. Despite this, the polymer concentration (Cpoly) of the trapped PDEA droplet was very low and was around 30 wt %. Cpoly depended on the molecular weight of PDEA and the laser power that regulates the temperature elevation. These results strongly indicate that PDEA undergoes coacervation in addition to a coil-to-globule phase transition. This study will help provide us with a fundamental understanding of the phase separation mechanisms of thermoresponsive polymers.

Protein phosphorylation and glycosylation, as two of the most important post-translational modifications of proteins, are of great significance to humans. The development of materials that can selectively enrich phosphopeptides and glycopeptides from complex biological samples has considerable value. In this work, an environmentally friendly bionic cellulose-derived monolithic material (TiPCM) with a coral-like structure was prepared using a thermally induced phase separation (TIPS) method and exhibited good hydrophilicity, a satisfactory porous structure, and a large quantity of titanium ions allowing it to simultaneously enrich both phosphopeptides and glycopeptides or enrich phosphopeptides alone from biological samples. The prepared TiPCM material could enrich phosphopeptides and glycopeptides, respectively, from a BSA/β-casein (molar ratio, 5000/1) and BSA/IgG (molar ratio, 1000/1) mixture demonstrating that it has excellent selectivity for phosphopeptides and glycopeptides. Meanwhile, it is worth mentioning that TiPCM materials show reusability in the enrichment of phosphopeptides, which has not been studied much in the literature. Moreover, three replicate analyses from 200 μg of tryptic digest of milk identified 119 unique phosphopeptides from 38 phosphoproteins, while identifying 180 glycopeptides from 93 unique glycoproteins and their corresponding 148 independent glycosylation sites. These results demonstrate the potential of TiPCM materials in the analysis of phosphorylated and glycosylated proteomics.

Hydroxyapatite (HA) shows promising applications in the clinical treatment of bone defects owing to its excellent physicochemical properties, such as biocompatibility, bioactivity, and osteoconductivity. However, it is difficult to maintain a porous structure in HA materials because of processing difficulties. In this study, a hard template method was developed to prepare a porous HA monolith with a hierarchical pore structure and high porosity. The cellulose monolith template was prepared from cellulose acetate using a thermally induced phase separation method. The cellulose monoliths were then immersed into the HA slurry to form a cellulose_HA composite monolith, which was converted to an HA monolith by burning in air to remove the cellulose monolith. Owing to the hierarchically porous structure of the cellulose monolith template, the obtained HA monolith demonstrated a hierarchically porous structure. Furthermore, the HA monolith was explored to study the adsorption and release properties of bovine serum albumin (BSA), which indicated that the HA monolith had a high adsorption capacity (388.6 mg g−1) and sustained release from the BSA-loaded HA monolith. Thus, HA monoliths have potential applications in the field of protein purification and biomaterials.

A cost-effective and facile method was developed for the fabrication of two polyimide-based (PI-based) monoliths (pure PI monolith and hybrid PI monolith) with a hierarchically porous structure that avoids the shortcomings of traditional methods. In this case, the thermally induced phase separation (TIPS) method was used to prepare polyamic acid (PAA) monoliths for the first time, then PI-based monoliths were fabricated by thermal imidization. Through the introduction of octakis(glycidyldimethylsiloxy)octasilsesquioxane into the PAA prepared from 4,4′-oxydianiline and pyromellitic dianhydride, both the hydrophobicity and mechanical strengths of the PI-based monoliths were improved. Moreover, the resulting PI-based monoliths exhibited suitable permeability, homogeneous morphologies, and superior thermal stability. Adsorption tests demonstrated that the resulting hybrid PI monoliths exhibited better adsorption performance for organic solvents and silicone oil than the pure PI monolith. Furthermore, the surface of a polyhedral oligomeric silsesquioxane (POSS) hybridized PI (PI-co-POSS) monolith can be modified into a hydrophilic layer by reaction between the hydrophilic polymer and epoxy groups exposed on the surface. This indicates that PI-co-POSS monoliths have potential in liquid diode application to achieve oil–water separation.

Cellulose-based functional materials have gained immense interest due to their low density, hydrophilicity, chirality, and degradability. So far, a facile and scalable preparation of fibrillated cellulose by treating the hydroxy groups of cellulose with citric acid (F-CAC) has been developed and applied as a reinforcing filler for polypropylene composite. Herein, a size-selective preparation of Au nanoparticles (NPs) stabilized by F-CAC is described. By modifying the conditions of transdeposition method, established in our group previously, a transfer of Au NPs from poly(N-vinyl-2-pyrrolidone) (PVP) to F-CAC proceeded up to 96% transfer efficiency with retaining its cluster sizes in EtOH. Meanwhile, the deposition efficiency drastically decreased in the case of nonmodified cellulose, showing the significance of citric acid modification. A shift of binding energy at Au 4f core level X-ray photoelectron spectroscopy from 82.0 to 83.3 eV indicated that the NPs were stabilized on an F-CAC surface rather than by PVP matrix. The reproducible particle size growth was observed when 2-propanol was used as a solvent instead of EtOH, expanding the range of the available particle size with simple manipulation. The thus-obtained Au:F-CAC nanocatalysts exhibited a catalytic activity toward an aerobic oxidation of 1-indonol in toluene to yield 1-indanone quantitatively and were recyclable at least six times, illustrating high tolerance against organic solvents.

Metal oxide affinity chromatography (MOAC) is considered to be one of the most effective methods for phosphopeptide enrichment. However, most of the materials used in the method are powder; frequent centrifugation is necessitated during the enrichment process, and potential risks of loss of peptides and materials and clogging of the column employed for liquid chromatography-mass spectrometry (LC-MS) arise. Moreover, the reusability of these materials to achieve sustainability was hardly investigated. To overcome these limitations, herein, inorganic titanium dioxide (TiO

We developed a mechano-responsive hydrogel that is driven by the dissociation of a host-guest complex. The hydrogel comprised a thermoresponsive linear polymer with adamantane as a guest molecule in its side chain and a nonthermoresponsive network structure with β-cyclodextrin as a host molecule. Immobilization of the thermoresponsive polymer in the hydrogel via host-guest interaction resulted in a partial restriction of its phase transition, even above its lower critical solution temperature (LCST). The hydrogel demonstrated a decrease in transmittance when mechanical stress was applied at a temperature above its LCST, indicating that the phase transition of the thermoresponsive polymer was induced by the dissociation of the host-guest complex under mechanical stress. Moreover, this mechano-responsive behavior was repeatable by cooling the hydrogel to redissolve the thermoresponsive polymer. The strategy of the mechano-responsive phase transition will be useful for various applications that demand the control of desired functions by applied stress.

Biocompatible hydrogels are considered promising agents for application in bone tissue engineering. However, the design of reliable hydrogels with satisfactory injectability, mechanical strength, and a rapid biomineralization rate for bone regeneration remains challenging. Herein, injectable hydrogels are fabricated using hydrazide-modified poly(γ-glutamic acid) and oxidized chondroitin sulfate by combining acylhydrazone bonds and ionic bonding of carboxylic acid groups or sulfate groups with calcium ions (Ca

Recently, several studies have reported using an oxidation method, such as plasma, to introduce polar functional groups to the polymer surface. However, these methods are difficult to use to oxidiz...

A facile method is reported to fabricate a flow reactor from natural wood, in which gold nanoparticles are generated and stabilized using the wood itself as reductant and stabilizer in a continuous...

Thermoresponsive phase separation mechanisms of aqueous poly(N-isopropylacrylamide) (PNIPAM) solutions were investigated using an optical tweezer combined with a Raman microspectroscope. A near-inf...

Hydrogels are biocompatible polymer networks; however, they have the disadvantage of having poor mechanical properties. Herein, the mechanical properties of host-guest hydrogels were increased by adding a filler and incorporating other noncovalent interactions. Cellulose was added as a filler to the hydrogels to afford a composite. Citric acid-modified cellulose (CAC) with many carboxyl groups was used instead of conventional cellulose. The preparation began with mixing an acrylamide-based αCD host polymer (p-αCD) and a dodecanoic acid guest polymer (p-AADA) to form supramolecular hydrogels (p-αCD/p-AADA). However, when CAC was directly added to p-αCD/p-AADA to form biocomposite hydrogels (p-αCD/p-AADA/CAC), it showed weaker mechanical properties than p-αCD/p-AADA itself. This was caused by the strong intramolecular hydrogen bonding (H-bonding) within the CAC, which prevented the CAC reinforcing p-αCD/p-AADA in p-αCD/p-AADA/CAC. Then, calcium chloride solution (CaCl

Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH) is one of the biomass plastics synthesized by intracellular fermentation of plant oils and saccharides, which has good flexibility and mechanica...

To improve the mechanical properties of biodegradable bioplastic poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH), a filler made up of silica particles (SiO2) is mixed with PHBH; however, SiO2 ...

The development of tough, self-healing materials is a notable accomplishment. Previously, self-healable materials were soft materials with a tensile stress less than 10 MPa. Herein, we describe cit...

Surface geometries in nature such as wrinkle structures have various functions. Attention has been paid to the fabrication method of the geometry and geometry control by external stimuli. This is because surface geometries as an active interface are able to contribute to the control of interactions with the external environment. In this study, aligned wrinkles were fabricated on the surface of stretched hydrogels in aqueous conditions by the electrophoretic formation of a polyion complex layer. The geometry of wrinkles was controlled by the stretching ratio and Young's modulus of hydrogels, and hierarchical wrinkle structures were fabricated after unloading the stretched hydrogels. Therefore, it can be a new wrinkle-formation method capable of transferring the initial elastic anisotropy of the substrate material to the wrinkle structure. Creation of thermoresponsive wrinkles that can transform their geometrical configuration reversibly was achieved by fabrication of aligned wrinkles on the surface of thermoresponsive hydrogels.

This study reports pollutant remediation by a catalyst-loaded, β-cyclodextrin cross-linked polymer monolith. The monolith enabled removal of the pollutant to a residual concentration with no environmental effect and conversion of the adsorbed pollutant into useful compounds with enriched concentration, allowing for the adsorption capacity regeneration.

A novel cellulose monolith supported ZIF-8 metal organic framework as a hierarchical porous material was designed by using a highly effective pump injection method, which is used for a flow-based reaction.

In this study, we contribute the facile fabrication of tough polyolefin monoliths from their polymer solutions using a phase separation method. Compressive stress–strain tests demonstrate that the monoliths have excellent mechanical properties. The monoliths show macroporous structures where the pore sizes can be tuned from sub-1 to 16 µm by adjusting the fabrication conditions. The monoliths exhibit high hydrophobicity/ oleophilicity and good resistance toward different chemicals. Based on the above properties, we applied the monoliths to the selective absorption of oil from an oil/water mixture. By simply squeezing the monoliths, the absorbed oil can be recovered. The monoliths are useful for more than 10 cycles of absorption and recovery, showing a good stability for industrial-scale oil spill treatment.

The dynamic and static properties of structured surfaces have important functions in nature. In particular, wrinkles have important static roles, for example, increasing surface area, but dynamic roles of wrinkles remain poorly understood. Specifically, to understand and utilize the dynamic functions of wrinkles, it is necessary to observe wrinkle formation directly. In this study, a polyion complex (PIC) is formed on a hydrogel surface by electrophoresis, and the process of wrinkle formation through a transparent electrode is directly observed. By quantitative analysis of the wavelength and amplitude of wrinkles, it is found that the wrinkles move randomly in a wavy pattern in the initial stage of growing process. Furthermore, the direction of wavy motion of wrinkles is controlled by the compression of hydrogels in the in-plane direction. The present study provides important insights into the fabrication of wrinkled surfaces with a controlled flow direction; opening the possibility for active wrinkles used in the development of functional surface structures as actuators that are capable of transporting small objects in water.

Owing to their unique properties, hydrogels may be used for preparing soft actuators. Soft actuators are expected to respond quickly; however, the response speed of gels is slow. To study this issue and overcome it, thermoresponsive soft actuators were prepared by the electrophoretic adhesion of cationic and anionic thermoresponsive microgels, comprising poly(diallyldimethylammonium chloride) and poly(styrenesulfonate) sodium salt, respectively. The kinetics of the prepared hydrogel architectures in response to temperature depended on the microgel diameter instead of the architecture size. We also prepared bilayered hydrogel architectures by adhesion of thermoresponsive and/or nonthermoresponsive microgels. These bent rapidly in response to temperature because these architectures consisted of microgel assemblies. In addition, specific bending motion was demonstrated by the adhesion of microgel layers of different sizes. The present study provides not only a guideline for the design of hydrogel actuators with quick response but also presents a method for the free-form fabrication of functional hydrogel materials that undergo complex motions in response to stimuli.

The present study reported the flexible and highly efficient one-step synthesis of chiral hierarchical porous monoliths via cross-linking and polymerization-induced phase separation using substituted acetylene and cross-linker in the presence of porogenic solvent (tetrahydrofuran and methanol) in which the complex doping and complicated procedures were not required. It was demonstrated that hierarchical pore structure with through-pore and high surface area existed in the monoliths, which provides more chiral sites and space for interaction between monolithic materials and the solution. The porous structures and pore size can be adjusted by changing the conditions of phase separation. Moreover, the prepared monoliths exhibited good optical activity, thermal stability and mechanical properties. Therefore, the hierarchically porous monoliths with optical activity were applied in enantioselective crystallization and showed good performance.

An ultralight bacterial cellulose/polypropylene-graft-maleic anhydride (BC/PP-g-MA) composite cryogel was fabricated using a facile temperature induced phase separation (TIPS) method followed by fr...