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This study examined the effect of the surface charge of concentrated polymer brush (CPB)-grafted cellulose nanofibers (CNFs) on HepG2 cell flocculation. Four polyelectrolytes, poly(

Cellulosic bottlebrushes with polystyrene (PS) and poly(ethylene glycol) (PEG) side chains at the O-6 and O-2, 3 positions, respectively (PEG-PS-cellulose), were synthesized and characterized in diluted solution to reveal the second structure of heterografted bottlebrushes. The regioselectivity and degree of substitution were evaluated by 1H- and 13C-nuclear magnetic resonance spectroscopy and size-exclusion chromatography (SEC). The cross-sectional structure of PEG-PS-cellulose was evaluated from the cross-sectional radius of gyration determined by the small angle X-ray scattering technique as a function of the molecular weight of the PS side chain. As a result, PEG-PS-cellulose was found to show a core-shell-corona structure, in which PEG and PS side chains formed a homogeneous shell layer surrounding the cellulosic core and the outer segments of PS chains formed an outer corona layer. The stiffness parameter (λ−1) of the main chain was analyzed by the SEC–multiangle light scattering technique along with the Kratky-Porod wormlike chain model. In comparison with a previously reported cellulosic bottlebrush with a PS side chain at the O-6 position, it is suggested that the observed increase in λ−1 with increasing molecular weight of PS is mainly derived from the interaction among PS side chains located in an outer layer, while the PEG side chains at the O-2, 3 position effectively suppressed the internal rotation of the cellulosic main chain.

In this study, concentrated polymer brush-modified cellulose nanofibers (CNFs) with different fiber lengths were used for the flocculation of cells for systematically studying the mechanism of this unique cellular flocculation based on colloidal flocculation theory. Concentrated poly(

In order to develop new three-dimensional (3D) cell culture systems for articular cartilage regeneration, concentrated poly(styrene sulfonate sodium salt) brush-modified cellulose nanofibers were employed as building blocks for the self-assembly of human mesenchymal stem cells (hMSCs). Unique 3D cellular structures, such as giant spheres and sheets, were formed by controlling hMSC self-assembly.

We developed a novel electrochemical biosensor electrode that has a potential to reduce background noise for which we constructed an original conductive substrate modified with a double-layered polymer brush structure that is water impermeable and can control biomolecules adsorption/desorption. In this study, a hydrophobic poly(tert-butyl methacrylate) brush layer was prepared on a gold electrode, and then, the tert-butyl group near the outermost surface was dissociated by the acid treatment to obtain a hydrophilic carboxy group, thereby fabricating a conductive substrate with the double-layered polymer brush structure. Formation of the double-layered polymer brush structure was indicated by surface wettability and optical analyses. The potential difference and hydrogen ion concentration, which is a typical parameter of the surrounding environment, were linearly correlated with the gold electrode having a double-layered polymer brush structure with carboxyl groups. However, there was no correlation on gold electrodes with self-assembled monolayers presenting carboxy groups. It is considered that the pH responsiveness of the carboxy groups on the outermost surface could be exhibited remarkably because the charge state in the vicinity of the surface became constant due to the hydrophobic polymer brush layer having a certain thickness. The target DNA could be captured more efficiently at the probe DNA-immobilized electrode with the double-layered polymer brush structure than when using COOH-SAM. This is the first report of the application of the double-layered polymer brush structure for the electrochemical biosensing, and it will be an excellent surface modification method to reduce background noise.

In this article, we describe the synthesis and self-assembly of novel Janus bottlebrushes with cellulose as a polymeric backbone. The cellulosic Janus bottlebrushes, bearing poly(e-caprolactone) (PCL) and polystyrene (PS) branches at the C-2,3 and C-6 positions of anhydroglucose units, respectively, were successfully prepared using a bulky p-methoxytrityl protecting group and by combining the “grafting-from” ring-opening polymerization of e-caprolactone with the “grafting-to” click chemistry of PS. The degree of substitution of PCL at the C-2,3 positions was estimated to be 1.5, whereas values of 0.64–0.84 were estimated for the C-6 position of PSs with different molecular weights (number-average molecular weight = 4.0, 9.2, or 16 kg mol−1), depending on the length of the PS graft. The Janus bottlebrushes (PS/PCL = 50:50 v/v) self-assembled to form a lamellar microdomain structure comprising three layers (amorphous PCL, crystalline PCL, and amorphous PS layers), as characterized by small-angle X-ray scattering and transmission electron microscopy. The interlamellar distance was approximately 30 nm, depending on the length of the PS graft. The results illustrate that cellulosic polymeric backbones for Janus bottlebrushes can exhibit microscale morphologies, potentially leading to the development of polymers with new morphologies and functionalities.

Lithium-excess layered positive electrodes containing Fe and Ni are promising materials for the next generation of high voltage lithium ion batteries (LIB) because they are more chemically stable t...

Very-thick, concentrated brushes of poly(methyl methacrylate) (PMMA) were synthesized by surface-initiated atom transfer radical polymerization in N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium bi...

Fullerene-containing polymers offer the unique opportunity to fabricate self-assembled nanostructures and organic electronics. The synthesis of well-defined fullerene-containing polymers, having double polymeric chains attached to fullerene in a regioselective manner, is a fundamental challenge in both synthetic organic chemistry and precision polymer chemistry. Here, inspired by the state-of-the-art fullerene chemistry, we present a new strategy for the stepwise synthesis of double-armed polymers with fullerene C60 at the junction in high reaction yields and with high selectivity. First, poly(styrene)-attached 1,2-hydrofullerene (1,2-PS-C60-H) was synthesized via the cobalt-catalyzed radical addition reaction. Next, the fullerenyl anion, 1,2-PS-C60−, was reacted with bromo-terminated poly(acetoxystyrene) to generate diblock copolymer 1,4-bisadducts (1,4-PS-C60-PAS). This example highlights the applicability of polymeric 1,4-fullerene bisadducts for self-assembling building blocks and potential organic electronics.

The synthesis of ultrathick concentrated poly(methyl methacrylate) (PMMA) brushes by atom transfer radical polymerization (ATRP) was investigated. The reactions were performed with a catalyst syste...

In this article, we describe the conformational characteristics of a cellulosic bottlebrush, i.e., a cellulose derivative of densely substituted side chains, in a dilute solution in order to clarif...

Recently, concentrated polymer brushes (CPBs) have attracted much attention as potential tribomaterials showing an ultralow friction coefficient (e.g., 10−4 in a microtribological analysis)...

The degree of chain-end functionality in a densely grafted, concentrated polymer brush is a critical parameter. In this study, p-polarized multiple-angle incidence resolution spectrometry (pMAIRS) ...

Bacterial cellulose (BC) has a well-defined nanofiber network in the gel, potentially applicable as a reinforcement filler for ideal polymer composite materials. In this study, BC/poly(methyl metha...

Concentrated polymer brushes (CPBs) are promising soft-material coatings for improving tribological properties under severe sliding conditions, even in the macroscopic scale. Therefore, they are expected to be applied to mechanical sliding components. However, the durability of CPBs has remained challenging for industrial applications. Previous studies revealed that applying a groove texture to the CPB substrate is effective in improving the durability of CPBs. In order to achieve further improvement of durability of CPBs, we attempted to apply nano-periodic structures, whereas the groove texture applied in previous studies has widths and depths in micrometres. In this study, the effect of the nano-periodic structure in addition to the groove texture applied to the CPB substrate on the durability of CPB is investigated. The results demonstrate a significant improvement in the durability of CPBs by up to 90% compared with non-textured CPB when an appropriate nano-periodic structure is applied (i.e. a nano-periodic structure oriented parallel to the groove texture).

Concentrated polymer brushes (CPBs) are known to suppress biofouling phenomena, such as protein adsorption and cell adhesion. However, a cumbersome process is needed for their synthesis. Here, we report a simple and versatile method for fabricating nonbiofouling coatings that uses well-defined bottlebrushes instead of CPBs. First, a macroinitiator, poly[2-(2-bromoisobutyryloxy)ethyl methacrylate] (PBIEM), was synthesized by reversible addition-fragmentation chain transfer polymerization. Then, poly[poly(ethylene glycol) methyl ether methacrylate] was grafted from PBIEM through atom transfer radical polymerization to form well-defined bottlebrushes. By controlling the graft chain length, two types of bottlebrushes could be prepared, namely those with a semi-dilute polymer brush (SDPB) structure or a CPB structure on the surface of the outermost layer. Crosslinked films of the bottlebrushes were prepared on silicon wafers by spin-coating and subsequent radical coupling. Importantly, the CPB-type bottlebrush films showed significantly better nonbiofouling characteristics than those of the SDPB-type bottlebrush films.

Concentrated polymer brushes (CPBs) are promising soft-material coatings for improving tribological properties under severe sliding conditions, even in the macroscopic scale. Therefore, they are expected to be applied to mechanical sliding components. However, the durability of CPBs has remained challenging for industrial applications. Previous studies revealed that applying a groove texture to the CPB substrate is effective in improving the durability of CPBs. In order to achieve further improvement of durability of CPBs, we attempted to apply the periodical structure, which is a microfabricated structure corresponding to a surface roughness 0.02 μm, whereas the groove texture applied in previous studies has widths and depths in micrometres. In this study, the effect of the nano-periodic structure in addition to the groove texture applied to the CPB substrate on the durability of CPB is investigated. The results demonstrate a significant improvement in the durability of CPBs by up to 90% compared with non-textured CPB when an appropriate nano-periodic structure is applied (i.e. a nano-periodic structure oriented parallel to the groove texture).

Production of nanocomposites from macro-scale materials in situ in a melting compounder is highly desirable yet challenging. In this study, we develop a highly efficient approach for the preparation of cellulose nanofiber (CNF)-reinforced high-density polyethylene (HDPE) composite materials from as-received wood pulp fibers, in which nanofibrillation-assisting plasticizers (urea and urea derivatives) and a diblock copolymer dispersant are used. The most effective plasticizer is urea, which plays a crucial role in producing CNF with less fragmentation during the kneading step, owing to the plasticization/nanofibrillation and the reaction with hydroxyl groups of cellulose fibers into a carbamate. The diblock copolymer as a dispersant enables the stabilization of the appropriate dispersion of the produced CNF in nonpolar HDPE. The resulting composites exhibit significantly improved mechanical properties, including a 6.9-fold increase in the Young’s modulus with 10 wt % loading of wood pulp fibers over that o...

A new type of three-dimensional cell culture using a cellulose nanofiber modified with a concentrated polymer brush (CNF-CPB) is described from the viewpoint of colloidal flocculation. By varying the CNF-CPB concentrations from 0.005 to 0.5 wt %, we demonstrate that hepatocyte cells self-assemble with the CNF-CPBs and change the floc size and shape (fully filled or hollow) in a concentration-dependent manner. A protein adsorption test indicates that affinity interaction between the proteins (cells) and CPB is critical for cellular flocculation. In addition, gene expression analysis confirms that the cellular flocs using CNF-CPBs enhance cell functions compared to CNFs with semidilute polymer brushes and pristine CNFs.

In this article, the conservation of archaeological waterlogged wood (WW) of Afzelia sp. (medium degraded: Umax = 385%) was impregnated in vacuum with an aqueous solution of acrylic acid (AA), sodium acrylate monomer (AANa), crosslinking agent (MBA) and catalyst (V-501). The simultaneous in situ polymerization and crosslinking resulted in slightly crosslinked sodium polyacrylate (PAANa) in the wood structure. The results showed that untreated WW had only a very limited ability to re-swell to recover its original dimensions from a collapsed condition, while WW protected by crosslinked PAANa could almost fully recover its original shape and size even after several drying–rewetting cycles. From microscopic observations, treated wood was found to maintain its original cell structure, form and shape even after repeated drying–rewetting cycles. PAANa was observed to be densely localized near the middle lamella, the cell corners, and the cell lumina by transmission electron microscopy observation. These observations suggest that our PAANa treatment provides reasonable strength as well as favorable hydrophilicity to avoid hornification of the cell wall upon drying, thus providing unique shape recovery properties.

Epoxy resin-based monoliths, possessing a bicontinuous structure that consists of a porous channel and a resin skeleton, have a broad range of applications such as chromatography; however, the preparation of spherical particles has been limited so far. This is the first report on a versatile and facile preparation method for surface-skinless monolithic particles with micrometer diameters by polymerization-induced phase separation in an oil-in-oil emulsion system. The key to success is the addition of a well-defined block copolymer surfactant, compatible for both the dispersed and continuous phases in suspension polymerization. In essence, the volume ratio and length of the block copolymers are crucial to control the stability of the emulsion and the suppression of the unwanted skin layer on the surface of the produced particles. The present work represents a new direction for versatile and large-scale preparation of monolithic particles, including silicates and polyacrylates, with several surface properties.

Cellulose nanofibers (CNFs) hold great potential as sustainable reinforcement fillers with excellent mechanical, thermal, and chemical properties. However, in polyolefin nanocomposite materials, the rational control of dispersion and the improvement of interfacial strength remain challenging. Herein we propose the tuning of the interface between CNF and high-density polyethylene by the design of polymer dispersants on the basis of surface free energy and the glass transition temperature. The former is related to the wettability against the polymer matrix and is therefore critical to the dispersion of CNF whereas the latter is related to the interfacial strength between CNF and HDPE. As a result of this investigation, we discovered a suitable dispersant for CNFs, poly(dicyclopentenyloxyethyl methacrylate)-block-poly(2-hydroxyethyl methacrylate), which played a pivotal role in achieving both a uniform dispersion of CNF and greatly improved mechanical properties, including a 4-fold increase of the Young's modulus over that of neat HDPE with 10 wt % CNF loading.

In this study, a one-side zero-anchoring in-plane switching (OZ-IPS) liquid crystal display that used an application-type, zero-azimuth anchoring material as a substitute for polymer brushes was successfully developed. The transmission efficiency of this OZ-IPS cell was also improved by optimizing its optical design.

Halogen exchange of alkyl bromide (R–Br) with sodium iodide (NaI) was used for the transformation of R–Br to alkyl iodide (R–I) in situ in organocatalyzed living radical polymerization (LRP). R–Br was employed as a starting compound (precursor), and the R–I formed in situ was employed as an initiating dormant species for the polymerization. The efficiency of the transformation significantly depends on the R group of R–Br. By the rational selection of the R group and reaction temperature along with the use of tetrabutylammonium iodide (Bu4NI) as a catalyst, low-polydispersity (Mw/Mn = 1.1–1.4) polymers were obtained with high conversions (e.g., 70–90%) in reasonably short periods of time (typically 3–10 h) in the polymerizations of methyl methacrylate, butyl acrylate, styrene, acrylonitrile, and functional methacrylates. Well-defined diblock and triblock copolymers and a chain-end functional polymer were also obtained. R–Br is generally much more stable than R–I upon storage. Various R–Br are commercially available. The use of simple, stable, and inexpensive R–Br as precursors of the dormant species is an attractive feature of this system. The high monomer versatility and the accessibility to a wide range of polymer structural designs demonstrated in this work show the capability of this system for use in a range of applications. Accepted version

A novel radio-wave exposure equipment system is developed for studies on thermal perception thresholds of biological effects exposed to millimeter-wave at 70 GHz band that is one of 5th generation wireless systems (5G) candidate frequency band. To achieve high duty RF exposure on living body at 70 GHz required, we newly designed a lens antenna that can irradiate focused beam. In order to obtain basic exposure performance of the developed equipment, we used physical phantom that simulated human's skin and achieved experimental measurements of temperature rise during at 70 GHz band millimeter-wave exposure. After 60 seconds exposure, the temperature on expected area of the phantom surface increased 0.6 degree Celsius. In summary, developed equipment can achieve required high exposure on the sample.

A millimeter-wave (MMW) at 28 GHz band, a candidate frequency for 5th generation wireless systems (5G), causes some concern about possible adverse effects on the human body. To investigate biological effects of local exposure to MMW, exposure systems equipped with a newly lens antenna, that can irradiate focused beam, were developed and characteristics of exposure for the skin were evaluated. The basic exposure performance of the systems was evaluated using temperature monitoring in physical phantom simulated human's skin and actual skin of forearm. Local temperature elevations were observed in both exposed skins, meaning achievement of results we expected in dosimetry. However, the time courses of these elevations were significantly different. These results suggest that some elements related to the temperature control such as heat conductivity and cooling by skin blood flow should be considered.

In this article, we propose a versatile method to prepare epoxy resin-based monolith membrane without any surface skin layer through polymerization induced spinodal type phase separation using a poly(vinyl alcohol) sacrificial film, where the monolith is a porous material with a bicontinuous skeletal structure. The resulting monolith membranes exhibit well-defined pore sizes, and high mechanical strength, thermal stability, and ionic conductivity in liquid electrolytes. A block copolymer has been applied to control the pore size to be at the mesoscale, and surface skinless freestanding monolith membrane have been developed. To improve the mechanical properties, cellulose nanofibers are introduced as a reinforcing filler. The monolith membranes are thermally resistant at least up to 200 °C. The ionic conductivity of the monolith membranes (0.71 mS cm−1 at 25 °C) is comparable to those of commonly used polyolefin separators. The results that are presented here demonstrate that polymer monolith membranes have bright prospects as novel separators for lithium ion batteries, fuel cells, etc.

Various Langmuir–Blodgett (LB) films of tetraphenylporphyrin (TPP)-bound acyl celluloses with different degrees of substitution of the TPP groups (DSTPP) and different acyl groups were prepared. TPP-bound acyl celluloses with DSTPP values less than 0.38 and myristoyl groups as the O-2 and O-3 substituents were suitable for obtaining LB mono-layer films with high quantum yields. The horizontal lifting method was better than the vertical dipping method for the deposition of LB films. The number of layers in LB multi-layer films of TPP-bound myristoyl cellulose with a DSTPP of 0.36 also influenced the quantum yield, and the quantum yield of the LB di-layer film was higher than those of the LB mono- and tri-layer films. This information will be useful in the improvement of the photocurrent generation performances of LB films of TPP-bound acyl celluloses.

An effective approach for the dispersion of hydrophilic cellulose nanofiber (CNF) in hydrophobic high-density polyethylene (HDPE) is presented using adsorption of a diblock copolymer dispersant. The dispersant consists of both resin compatible poly(lauryl methacrylate) (PLMA) and cellulose interactive poly(2-hydroxyethyl methacrylate) blocks. The PLMA-adsorbed CNFs are characterized by FT-IR and contact angle measurement, revealing successful hydrophobization. X-ray CT imaging shows there are apparently less CNF aggregates in the nanocomposites if adding amount of the dispersant was enough. The good dispersion results in a high mechanical reinforcement, corresponding to 140% higher Young's modulus and 84% higher tensile strength than the neat HDPE. This approach is broadly applicable and allows for easy manufacturing process for strong and lightweight CNF-reinforced nanocomposite materials.

We developed a novel and practical assessment technique for endoglucanase (EG) activity by measuring the degree of polymerization (DP) of cellulose from Eucalyptus globulus. This evaluation method demonstrated that EG II from Trichoderma reesei had higher endoglucanase activity than EG I, which has not been detected in conventional experiments using carboxymethyl cellulose as a model substrate. In addition, a high-throughput protocol for DP measurement was developed by using near-infrared spectroscopy combined with a multivariate analysis. Interpreting the regression coefficient, a reciprocal correlation was observed between the relative crystallinity of the cellulosic residue after enzymatic hydrolysis and the DP.

The RF exposure guidelines do recognize that an increased local SAR (Specific Absorption Rate) due to metallic implants is possible. In this study, the effect of implantable medical device in human torso region is examined. A simple flat torso phantom is used which a cardiac pacemaker model is implanted in. The local SAR dependencies due to exposure frequency bands were presented. Here, we estimate localized SAR at several candidate frequency bands for 5th generation wireless systems.

Photocontrolled surface-initiated reversible complexation mediated polymerization (photo-SI-RCMP) was successfully applied to fabricate concentrated polymer brushes with complex patterning structures. Positive-type patterned polymer brushes were obtained by photo-SI-RCMP under visible light (550(±50) nm) using photomasks. A particularly interesting finding was that negative-type patterned polymer brushes were also obtainable in a facile manner. A nonspecial UV light (250-385 nm) enabled the preparation of pre-patterned initiator surfaces in a remarkably short time (1 min), leading to negative-type patterned polymer brushes. Based on this unique selectivity between visible and UV light, the combination of two patterning techniques enabled the preparation of complex patterned brushes, including diblock copolymers, binary polymers, and functional binary polymers, without multistep immobilization of one or more initiators on the surfaces.

Charged substrates are expected to promote cell adhesion via electrostatic interaction, but it remains unclear how cells adhere to these substrates. Here, initial cell adhesion (30 min) was re-examined on charged substrates in serum-containing and serum-free media to distinguish among various cell adhesion mechanisms (i.e., electrostatic interaction, hydrophobic interaction, and biological interaction). Cationic and anionic methacrylate copolymers were coated on nonionic nontissue culture-treated polystyrene to create charged substrates. Cells adhered similarly on cationic, anionic, and nonionic substrates in serum-free medium via integrin-independent mechanisms, but their adhesion forces differed (anioniccationicnonionic substrates), indicating that cell adhesion is not mediated solely by the cells' negative charge. In serum-containing medium, the cells adhered minimally on anionic and nonionic substrates, but they adhered abundantly on cationic substrates via both integrin-dependent and -independent mechanisms. These results suggest that neither electrostatic force nor protein adsorption is accountable for cell adhesion. Conclusively, the observed phenomena revealed a gap in the generally accepted understanding of cell adhesion mechanisms on charged polymeric substrates. A reanalysis of their mechanisms is necessary.

A series of novel mono- and bis[(9-alkylcarbazol-3-yl)methyl]acrylamides were synthesized and their radical polymerization was investigated. Emissions of bis(carbazolyl)acrylamide polymers were ext...

Hydrophilic epoxy resin-based monoliths were employed as cell culture substrates. The monoliths were made of a porous material with a bicontinuous structure that consisted of a porous channel and a resin skeleton. Monolith disks were prepared with a skinless surface through polymerization-induced spinodal decomposition-type phase separation. The pore sizes, which were well controlled by the polymerization temperature, ranged from 70 to 380 nm. The quantity of protein adsorbed per unit area and the early-stage adhesion of HepG2 cells on the monolith substrates were independent of pore size, meaning they were not affected by surface topology. Long-term cell adhesion, as indicated by adherent cell number and shape, as well as liver-specific gene expression were significantly affected by pore size. In terms of cell shape, number, and gene expression, pores of approximately 200 nm were most suitable for HepG2 cell growth. These results highlight the importance of monolith morphology for use as a cell culture substrate. The well-controlled morphology demonstrated in this work indicates monoliths are capable of supporting growth for various types of cells in a range of applications.

In this study, a one-side zero-azimuth anchoring in-plane switching (OZ-IPS) liquid crystal display (LCD) employing poly(n-hexyl methacrylate) (PHMA) bottlebrush polymers as an application-type zero-azimuth anchoring material was successfully developed. The twist anchoring coefficient A 2 measured for the nematic liquid crystal (NLC) on the PHMA bottlebrush at 25??C was comparable to that of the same NLC on high-density PHMA brushes. Optimizing the optical design increased the transmission efficiency (TE) of the OZ-IPS cell with the negative NLC to 95%, which was significantly higher than that of conventional IPS cells. Using optical simulation, the OZ-IPS LCDs with a negative NLC clearly exhibited the highest TE (107% of TN LCDs) for LCDs developed thus far. Moreover, the higher transmittance of the OZ-IPS LCDs was also confirmed for the practical TFT LCD, which exhibited a maximum luminance that was 30% higher than conventional IPS TFT LCDs.