Selective fabrication of hollow and solid polysaccharide composite fibers using a microfluidic device by controlling polyion complex formation Polym. J. (IF 2.17) Pub Date : 2018-07-19 Kazutoshi Iijima, Shun Ohyama, Kazuya Yuyama, Atsushi Shono, Mineo Hashizume
Natural polysaccharides are an important class of biomaterials that have attracted significant research interest for biomedical applications because of their high biocompatibility, biodegradability, and bioactivity. In this work, we fabricated water-insoluble composite hollow and solid fibers made of polyion complexes of chondroitin sulfate C (CS) and chitosan (CHI) using a single microfluidic device. A coaxial two-phase microfluidic device was constructed from stainless-steel needles and glass fibers, and CHI solutions and CS solutions were continuously infused into the core and sheath channels, respectively. The obtained fibers were flexible and homogeneous and had diameters of a few hundred micrometers. Hollow fibers were formed using water as the solvent of CS, while core-filled solid fibers were obtained using 20% (v/v) ethanol. The respective mechanisms for the fabrication of the hollow and solid fibers were discussed. An increase in the sheath flow rate or decrease in the core flow rate reduced the diameters of the fibers, while a reduction in the concentration of the CHI solution reduced the thickness of the hollow fibers. Furthermore, bovine serum albumin, used as a model protein, could be incorporated in the hollow and solid fibers by mixing them in the core flow solution. These results suggested the great potential of microfluidic techniques for the preparation of hollow and solid polysaccharide fibers.
Transition of phase-separated PBTPA/PMMA solution droplets from core–shell to Janus morphology under UV light irradiation Polym. J. (IF 2.17) Pub Date : 2018-07-17 Shu Kikuchi, Shinji Kanehashi, Kenji Ogino
Here, we report the morphological transition of a phase-separated structure from core–shell to Janus morphology in droplets consisting of a poly(4-butyltriphenylamine) (PBTPA)/poly(methyl methacrylate) (PMMA) blend solution, induced by UV light irradiation. We obtained a phase-separated structure formed by the evaporation of the solvent from polymer solution droplets dispersed in an aqueous solution containing a surfactant. The rate of transition decreased with increasing polymer concentration and diameter of the droplet. It was also found that the transition was caused by UV light with a wavelength of 365 nm, which is mainly absorbed by PBTPA, indicating that this phenomenon is triggered by PBTPA. When the droplet was heated to 75 °C, no transition was observed.
Solid-state polymerization of 1,4-bis(hexatriynyl)benzene derivatives Polym. J. (IF 2.17) Pub Date : 2018-07-17 Keita Sasamura, Kei Mizuguchi, Yoko Tatewaki, Shuji Okada
Two 1,4-bis(hexatriynyl)benzene derivatives with urethane groups, i.e., 10,10′-(1,4-phenylene)bis(5,7,9-decatriynyl N-(butoxycarbonylmethyl)carbamate) 1 and its perfluorophenylene derivative 2, were synthesized, and their solid-state photopolymerization was investigated. Upon UV irradiation, both of them showed excitonic absorption characteristic of polydiacetylene (PDA). In particular, 2 showed an absorption maximum at 743 nm, which was approximately 100 nm longer than that of conventional PDAs because of the effective conjugation between the polymer backbone and π-conjugated substituents. The conversion of 1 to the corresponding polymer was quite low. On the other hand, more than half of the hexatriynyl moieties of 2 were found to polymerize, indicating that most of the monomers were converted to the polymer upon prolonged UV irradiation.
Surface and interface designs in side-chain liquid crystalline polymer systems for photoalignment Polym. J. (IF 2.17) Pub Date : 2018-07-13 Shusaku Nagano
In side-chain liquid-crystal (SCLC) polymer systems, the liquid crystalline (LC) mesogenic groups preferentially orient normal to the substrate plane due to the excluded volume effect (homeotropic alignment). Photoresponsive azobenzene (Az) mesogens have a transition moment parallel to the molecular long axis. Light irradiation for photoreactions is generally applied perpendicular to the film surface. Therefore, a homeotropic orientation inhibits efficient photoreactions and photoalignments in Az SCLC polymer systems. This review focuses on new approaches to induce a random planar orientation in Az SCLC polymer systems by interface and surface molecular design. The mesogens in a high-density SCLC polymer brush formed by surface-initiated living radical polymerization adopt a random planar orientation. In the film of an SCLC block copolymer with an amorphous block, a random planar orientation is induced via surface segregation of either of the blocks. The random planar orientations of SCLC polymer systems are thermally stable and offer efficient in-plane photoalignment and photoswitching with hierarchical LC molecular architectures, forming, e.g., microphase-separated (MPS) SCLC block copolymers and layered polymer LC systems. These surface and interface molecular designs are expected to provide new concepts and possibilities for LC polymer devices.
Interfacial morphologies and associated processes of multicomponent polymers Polym. J. (IF 2.17) Pub Date : 2018-07-13 Hiroshi Jinnai
This review describes contemporary advancements in the study of interfacial morphologies and associated processes of multicomponent polymers. A particular emphasis is placed on the use of three-dimensional (3D) microscopy, for example, transmission electron microtomography (TEMT) and laser scanning confocal microscopy (LSCM). The time evolution of a spinodal interface during the phase separation of a polymer blend was followed by LSCM. The obtained 3D interfacial morphology was analyzed by differential geometry. The scalability was tested using curvature distributions. 3D nanoimaging, that is, TEMT, was applied to examine the stability and dynamics of complex block copolymer (BCP) morphologies, and novel structural data were directly assessed according to the 3D volume data. This review also examines two essential developments in the time-dependent in situ electron tomography of polymer materials to study the dynamic processes of BCPs. The 3D microscopy-based structural information renders an important perspective into the studies of nonlinear nonequilibrium occurrences as well as the statistical physics of long-chain-bearing moieties.
Direct arylation polycondensation for synthesis of optoelectronic materials Polym. J. (IF 2.17) Pub Date : 2018-07-13 Junpei Kuwabara
Direct arylation polycondensation has been investigated to develop efficient methods for the preparation of conjugated polymeric materials for use in optoelectronic applications. The reaction conditions have been examined to achieve high molecular weights and minimal structural defects in the recurring structures. Under optimal conditions, the direct arylation method has several advantages over conventional methods, e.g., it has fewer synthetic steps and yields a high-molecular-weight and high-purity polymer. The high-quality polymeric materials that were obtained exhibited superior performance to those obtained using a conventional method when used in optoelectronic devices such as organic photovoltaics and field-effect transistors. Recent developments in C–H/C–H coupling polycondensation are also described.
Size-tuned hydrogel network of palladium-confining polymer particles: a highly active and durable catalyst for Suzuki coupling reactions in water at ambient temperature Polym. J. (IF 2.17) Pub Date : 2018-07-12 Hikaru Matsumoto, Takanori Akiyoshi, Yu Hoshino, Hirokazu Seto, Yoshiko Miura
Poly(N-isopropylacrylamide)-based hydrogel particles (GPs) with different sized hydrogel networks were developed and used to confine a palladium (Pd) catalyst. The size of the gel network was tuned by varying the feed ratio of the cross-linking monomer. Nanosized-Pd(0) was loaded into the GPs, which contain a tertiary-amine ligand, via Pd-ion adsorption and subsequent reduction. The Pd-loaded GPs were used as the catalyst for a Suzuki coupling reaction between phenylboronic acid and 4-bromobenzoic acid in water at 30 °C. Due to the hydrophilic reaction platform provided by the hydrogel matrix of the GPs, the catalytic efficiencies of Pd-loaded GPs were significantly higher than those of commercially available Pd-loaded supports. Notably, the Pd-loaded GPs with the smallest gel networks were highly durable for Suzuki coupling reactions. It is plausible that the smaller network minimized or prevented the enlargement of Pd(0) during the catalytic cycle. The facile synthesis of the GPs, environmentally benign catalytic system, and high catalytic durability and activity of these Pd-loaded GPs are all important factors for the industrial application of these materials.
Advanced flavin catalysts elaborated with polymers Polym. J. (IF 2.17) Pub Date : 2018-07-10 Yukihiro Arakawa, Keiji Minagawa, Yasushi Imada
A variety of biological redox reactions are mediated by flavoenzymes due to the unique redox activity of isoalloxazine ring systems, which are found in flavin cofactors. In the field of synthetic organic chemistry, the term “flavin” is generally used for not only isoalloxazines but also related molecules including their isomers and some analogs, and those having catalytic activity are called flavin catalyst. Flavin catalysts are typically metal-free, and their catalytic activity can be readily accessed using mild terminal oxidants such as H2O2 and O2; therefore, redox reactions with these compounds have great promise as alternatives to reactions with conventional metal catalysts for the sustainable production of important chemicals. We recently became interested in using polymers for the development of flavin catalysts, especially to improve their practicality and advance the field of catalysis. Here, we summarize our recent research on such flavin–polymer collaborations including the development of facile preparation methods for flavin catalysts using polymers, readily reusable polymer-supported flavin catalysts, and flavin–peptide–polymer hybrids that can catalyze the first flavoenzyme-mimetic aerobic oxygenation reactions.
Grain coarsening on the free surface and in the thickness direction of a sphere-forming triblock copolymer film Polym. J. (IF 2.17) Pub Date : 2018-07-06 Rasha Ahmed Hanafy Bayomi, Konomi Honda, Isao Wataoka, Hideaki Takagi, Nobutaka Shimizu, Noriyuki Igarashi, Sono Sasaki, Shinichi Sakurai
Controlling a block copolymer “grain”, in which the microdomains are regularly ordered in a single lattice, is important for developing high-performance polymeric materials. This is because the grains, which are several micrometers in size, can directly affect the properties of the materials. In this regard, we focused on grain coarsening on the free surface and in the thickness direction of a sphere-forming triblock copolymer film. We evaluated the grain size on the free surface using atomic force microscopy combined with image processing, and in the thickness direction, we used small-angle X-ray scattering edge-view measurements. It was found that the grain growth in the direction parallel to the free surface was very slow in the early stage of thermal annealing. Then, the grain growth shifted to a rapid growth mechanism with a power-law relationship (grain size ~tα, with α = 0.7) after ~30 min. Based on the value of the growth exponent α, the grain growth mechanism is considered to fall between the random and deterministic processes. In contrast, for the thickness direction, a much larger value (α = 1.72) was obtained. For such a large α value, it is impossible to consider the growth mechanism of the grain within the conventional to framework of the growth of domains and droplets. Therefore, our results may require a new framework to explain the behavior of the grain growth in the spherical microdomain system. Another notable finding is that the thickness of the oriented layer near the free surface or near the surface in contact with the substrate can be as thick as 9.5 µm, which is substantially larger than the reported values of the propagation distance of surface-induced orientation of microdomains in block copolymers. Based on the results of the current study, it is speculated that grain growth serves as a propagator for the regular ordering of spherical microdomains and the orientation of the lattice.
Functional polymers from renewable plant oils Polym. J. (IF 2.17) Pub Date : 2018-07-05 Hiroshi Uyama
This focus review addresses recent progress on plant oil-based functional polymers and composites. Plant oils are one of the most ideal chemical feedstocks to replace fossil resources for a variety of industrial chemicals in the polymer industry. In this focus review, an environmentally benign coating system is demonstrated using plant oils as the starting substrate for the preparation of artificial urushi with high hardness and a high gloss surface. Epoxidized plant oils, mainly epoxidized soybean oil, are polymerized with designed inorganics, cellulose, and biodegradable aliphatic polyesters to afford functional biobased polymers and composites. Castor oil is used as the core of branched poly(lactic acid) to improve the physical properties of biobased plastics. These plant oil-based materials are significant for the molecular design of functional and high-performance biobased products for industrial applications to contribute to the reduction of greenhouse emissions.
Structure−property relationships of polypropylene-based nanocomposites obtained by dispersing mesoporous silica into hydroxyl-functionalized polypropylene. Part 2: Matrix−filler interactions and pore filling of mesoporous silica characterized by evolved gas analysis Polym. J. (IF 2.17) Pub Date : 2018-07-04 Ryota Watanabe, Hideaki Hagihara, Hiroaki Sato
Nanocomposites containing mesoporous silica (MPS) materials with various pore structures (SBA-15 and MCM-41 types) melt mixed into polypropylene (PP) or PP functionalized with hydroxyl groups (PPOH) were characterized by analytical pyrolysis techniques, such as evolved gas analysis (EGA)-mass spectrometry (MS) and heart-cut EGA-gas chromatography (GC)/MS, to evaluate the interactions between the polymer matrix and MPS and the pore filling of the MPS in the nanocomposite. The EGA-MS measurements revealed that nanocomposites with MPSs evolve specific degradation products, which can be attributed to strong interactions between the polymer molecules and the internal pores. The amount of these specific products increased upon increasing the pore size of the MPS and the hydroxyl content in the polymer matrix. Sufficiently large pores of MPS and high hydroxyl contents in the matrix appear to provide strong interactions because the MPS pores are well-filled with polymer molecules, which contributes to the improved physical properties of the nanocomposites.
Molar mass dependence of structure of xanthan thermally denatured and renatured in dilute solution Polym. J. (IF 2.17) Pub Date : 2018-07-03 Yasuhiro Matsuda, Kazuya Okumura, Shigeru Tasaka
Double helical polysaccharide, xanthan samples with varying molar mass were thermally denatured and renatured in dilute solutions. Both the weight average molar mass, which was determined by size exclusion chromatography (SEC), and viscosity average molar mass decreased after denaturation and renaturation for samples with an initial molar mass of 106 g mol−1, but those for the samples with an initial molar mass of 105 or 107 g mol−1 decreased only slightly. Although the double helices of xanthan only partially dissociated into single chains, the molar mass distribution estimated by SEC did not broaden drastically by the denaturation and renaturation. These results can be explained by the formation of hairpin structures by the single chains, which are restricted to xanthan with a molar mass of 105 g mol−1 by the strain of the hairpin loop, and for xanthan molar masses of 107 g mol−1 by the incomplete dissociation of its long polymer chains.
Structure-property relationships of polypropylene-based nanocomposites obtained by dispersing mesoporous silica into hydroxyl-functionalized polypropylene. Part 1: toughness, stiffness and transparency Polym. J. (IF 2.17) Pub Date : 2018-06-26 Ryota Watanabe, Hideaki Hagihara, Hiroaki Sato
The long-range objective of this study is to provide better understanding of the relationship between the structures and properties of PP-based nanocomposites containing mesoporous silica (MPS). In this investigation, nanocomposites composed of MPSs with various porosity structures (two types of Santa Barbara Amorphous No. 15 (SBA-15) with pores of 4.4 or 8.0 nm, and Mobile Composition of Matter No. 41 (MCM-41) with pores of 2.9 nm) and polypropylene (PP) or functionalized PP containing hydroxyl groups (PPOH) were developed. Their physical properties were then evaluated. The nanocomposite containing PPOH and SBA-15 with a large pore size (SBA-15-L) showed higher toughness, stiffness, and transparency than the other nanocomposites. Our results indicated that the larger pore size of SBA-15-L and the high affinity between PPOH and the MPS surface led to an efficient pore-filled state of SBA-15-L with polymer molecules, forming a nanocomposite with better mechanical strength and transparency.
Cocrystallization of monomer units of biobased and biodegradable Poly(l-lactic acid-co-glycolic acid) random copolymers Polym. J. (IF 2.17) Pub Date : 2018-06-20 Hideto Tsuji, Koudai Kikkawa, Yuki Arakawa
Random copolymers of l-lactic acid (LLA) and glycolic acid (GA) [P(LLA-GA)] with 0–100 mol% LLA units in the polymers were synthesized and their crystallization behavior was investigated by two representative crystallization methods of precipitation or melt-crystallization. P(LLA-GA) copolymers with LLA unit contents in the ranges of 0–20 and 73–100 mol% were crystallizable during precipitation or melt-crystallization. Surprisingly, these crystallizable ranges are similar to those reported for P(LLA-GA) copolymers synthesized by ring-opening polymerization of cyclic dimers (l-lactide and glycolide), which should have monomer sequence lengths twice those of the P(LLA-GA) copolymers synthesized by polycondensation of the monomers (LLA and GA) in the present study and are expected to have wider crystallizable ranges. The GA units of the LLA-rich P(LLA-GA) copolymers were incorporated in a lattice of LLA unit segments, whereas the LLA units of the GA-rich P(LLA-GA) copolymers were incorporated in a lattice of GA unit segments. Even the incorporation of relatively small-sized GA units in relatively large-sized LLA unit segments strongly induced structural disorder in the crystalline lattice. The crystalline size and melting temperature of the P(LLA-GA) copolymers decreased dramatically as the LLA unit content deviated from 0 to 100 mol%.
Preparation of polymer brushes with well-controlled stereoregularity and evaluation of their functional properties Polym. J. (IF 2.17) Pub Date : 2018-06-18 Tomoyasu Hirai, Masanao Sato, Tomoki Kato, Hitoshi Shimamoto, Kiyu Uno, Nobuyuki Otozawa, Atsushi Takahara
Polymer brushes in which one polymer chain end is tethered to a substrate show permanent properties related to the chemical structure of the polymer. However, they cannot accommodate functional molecules in the desired space because of the steric hindrance between neighboring polymer chains. To overcome this problem, the preparation of polymer brushes with ordered nanopores is strongly desired. High-density poly(methyl methacrylate) brushes with well-controlled stereoregularity were prepared using a surface-initiated living anionic polymerization method in the presence of a Lewis acid. A molecular weight range from 6 to 400 K with a narrow polydispersity index was obtained. Grazing incidence wide-angle X-ray diffraction measurements indicated that the polymer brushes formed a helical structure approximately 1 nm in diameter and consisting of encapsulated functional molecules or polymers, leading to the formation of inclusion complexes or stereocomplexes.
Polymers healed autonomously and with the assistance of ubiquitous stimuli: how can we combine mechanical strength and a healing ability in polymers? Polym. J. (IF 2.17) Pub Date : 2018-06-15 Chaehoon Kim, Naoko Yoshie
Among various approaches to create self-healing polymers, the introduction of dynamic bonds to polymers is one of the most powerful approaches. Macroscopic failure of such polymers is usually accompanied by the cleavage of dynamic bonds at the broken surfaces, which can then reform due to their reversible nature and repair the failure. However, since the reformation of dynamic bonds requires molecular mobility, autonomous healing at room temperature is almost completely limited to polymers with good molecular mobility, such as gels and soft elastomers. Mechanical strength usually conflicts with a high molecular mobility, as well as an autonomous healing ability. In this review, we first overview recent successful approaches to overcome this limitation. These approaches include combining careful dynamic bond chemistry choices and smart designs of the environment around the dynamic bonds. In the latter part of this review, attempts to design mechanically robust polymers that can heal with the assistance of ubiquitous stimuli are summarized. Such a healing process is a suboptimal choice for practical, valuable healing materials.
Preparation of an ethylene glycol-based block copolymer consisting of six different temperature-responsive blocks Polym. J. (IF 2.17) Pub Date : 2018-06-15 Yoko Kudo, Hiromitsu Mori, Yohei Kotsuchibashi
An ethylene glycol-based hexa-block copolymer with six different temperature-responsive blocks was prepared via a reversible addition-fragmentation chain transfer (RAFT) polymerization. 2-(2-methoxyethoxy)ethyl methacrylate (MEO2MA) and oligo(ethylene glycol) methacrylate (OEGMA) were selected as the ethylene glycol-based monomers. Each block of the hexa-block copolymer has a different OEGMA content and thus exhibits a different lower critical solution temperature (LCST). The structures of the block copolymers are similar to gradient copolymers. The molecular weights of the copolymers increased with the number of blocks (first block (P(MEO2MA)): 2800 g/mol, di-block copolymer: 7400 g/mol, tri-block copolymer: 12,000 g/mol, tetra-block copolymer: 18,500 g/mol, penta-block copolymer: 26,800 g/mol, and hexa-block copolymer: 40,400 g/mol) with relatively narrow molecular weight distributions (1.18–1.42). Each block exhibits a different LCST in aqueous solution owing to their different OEGMA contents. To the best of our knowledge, this is the first report of a block copolymer containing more than four types of temperature-responsive blocks. The temperature-responsive properties of the prepared block copolymers were investigated by UV-vis spectroscopy, micro-differential scanning calorimetry, and scanning electron microscopy.
Design and development of a robust photo-responsive block copolymer framework for tunable nucleic acid delivery and efficient gene silencing Polym. J. (IF 2.17) Pub Date : 2018-06-11 Thomas H. Epps III, Thu Vi, Millicent O. Sullivan
Nucleic acid delivery offers tremendous potential for the treatment of acquired and hereditary diseases. Despite limited successes, the use of nucleic acid therapies has been hampered by the lack of safe and efficient delivery approaches. To address this challenge, Epps, Sullivan, and coworkers developed a new nucleic acid delivery framework predicated on a photo-responsive cationic block copolymer (BCP) that enabled tunable nucleic acid binding and precise spatiotemporal control over gene expression. This innovative platform, in which the polymer moieties directly responsible for nucleic acid complexation could be cleaved from the polymer upon photo-stimulation, significantly enhancing nucleic acid release. Furthermore, temporal control over polyplex disassembly facilitated the development of a simple, and potentially universal, kinetic modeling scheme for intracellular small interfering RNA (siRNA), messenger RNA, and protein concentrations, and that model was quantitatively validated using various genes across several animal cell lines and human primary cells. This versatile BCP-based framework easily accommodated: anionic excipients that increased siRNA potency by ~200% (on a per mass basis) over comparable polyplex systems; quantum dots that unlocked theranostic applications without impacting silencing performance; and small-molecule lipid co-formulations that enhanced transfection in human primary cells. Altogether, the system described herein shows great promise for the clinical translation of gene therapeutics.
Photoinduced reinforcement of supramolecular gels based on a coumarin-containing gelator Polym. J. (IF 2.17) Pub Date : 2018-06-08 Kazuhiro Yabuuchi, Nanako Matsuo, Hiroshi Maeda, Masaya Moriyama
The mechanical strength of supramolecular gels is usually low compared to that of cross-linked polymer gels, which sometimes limits practical applications of supramolecular gels. We report here photoinduced reinforcement of supramolecular gel structures using photodimerization of coumarin moieties introduced on a trans-(1R,2R)-1,2-cyclohexanediamine-based gelator. UV irradiation (λ > 300 nm) of toluene gels containing mixtures of trans-(1R,2R)-1,2-cyclohexanediamine-based gelators with and without coumarin moieties induced an enhancement in both the thermal and mechanical stabilities of the gels.
On-demand easy peeling of acrylic adhesives containing ionic liquids through a microwave irradiation stimulus Polym. J. (IF 2.17) Pub Date : 2018-06-07 Mirei Usuba, Chizuru Hongo, Takuya Matsumoto, Takashi Nishino
We prepared microwave-responsive “on-demand-peeling” adhesives simply by mixing second-generation acrylic adhesives with ionic liquids. A rapid response (<30 s for adhesive failure) to microwave irradiation was achieved using a microwave oven. This “on-demand-peeling” was attributed to local heating of the ionic liquid in the adhesive by microwave irradiation. In addition, the adhesive strength was not influenced by the ionic liquid additives without microwave irradiation. We revealed that the local heating and the plasticizing effect of the ionic liquid were the cause of the “on-demand-peeling”. Our preparation method for these microwave-responsive adhesives is simple, conventional, and attractive for the fundamental and industrial fields.
Binding sites and structure of peptides bound to SiO2 nanoparticles studied by solution NMR spectroscopy Polym. J. (IF 2.17) Pub Date : 2018-06-07 Yu Suzuki, Heisaburo Shindo
Understanding the mechanism of the interaction between inorganic materials and peptides is important for the development of organic/inorganic hybrid materials. The titanium-binding peptide (TBP; Arg1-Lys2-Leu3-Pro4-Asp5-Ala6) has been reported to possess a high binding affinity to SiO2 as well as TiO2 surfaces. Here, we report the binding modes and mechanism of the TBP to SiO2 nanoparticles. To accomplish this objective, we analyzed the binding sites of the TBP to a SiO2 surface and the structure of the TBP bound to the SiO2 using solution NMR spectroscopy. Saturation transfer difference (STD) NMR analysis was performed to identify the TBP sites that interact with the SiO2 surface, and then Arg1 and Asp5 were identified to be in close contact with the SiO2 surface. The structure of the TBP bound to SiO2 was well defined, and the Arg1 and Asp5 side chains face in the same direction. The combination of these results validates that the guanidyl group of Arg1 and the carboxyl group of Asp5 interact electrostatically with the silanol groups SiO− and SiOH2+ on the SiO2 surface, respectively. The binding mode of TBP/SiO2 was found to be different from that of the TBP/TiO2 system, which has been previously reported.
Soft materials based on colloidal self-assembly in ionic liquids Polym. J. (IF 2.17) Pub Date : 2018-06-06 Kazuhide Ueno
Ionic liquids (ILs) have attracted much attention as dispersion media for colloidal systems as alternatives to organic solvents and electrolyte solutions. Although colloidal stability is an essential factor for determining the properties and performance of colloidal systems containing ILs, detailed mechanisms for colloidal stabilization have not yet been studied. In the first part of this paper, we highlight our fundamental studies on colloidal stability. Three different repulsive forces, electrostatic, solvation, and steric interactions, are examined for their effectiveness in stabilizing colloidal particles in ILs. In the second part of this report, we provide an overview of our recent studies on colloidal soft materials in the presence of ILs. On the basis of the suspended state of the silica colloid particles, two different soft materials, a colloidal gel and a colloidal glass, were prepared in ILs. Their functional properties, including ionic transport, rheological, and optical properties, are discussed in relation to the microstructures of the colloidal materials.
Synthesis and thermal investigation of phosphate-functionalized acrylic materials Polym. J. (IF 2.17) Pub Date : 2018-06-06 Yun-Fen Peng, Ashley Tsai, Ming-Hsi Huang
Functionalized acrylic materials derived from methyl methacrylate (MMA), 2-hydroxyethyl methacrylate (HEMA), and diethyl 2-(methacryloyloxy)ethyl phosphate (DMP) were synthesized by successive free-radical polymerizations using benzoyl peroxide (BPO) as the initiator and N,N-dimethyl-p-toluidine (DMpT) as the activator. NMR and GPC data showed that successful random copolymerization of MMA and DMP was carried out using the BPO-DMpT system. Moreover, the resulting products were able to react with HEMA monomer, yielding polymers with P(MMA-co-DMP)-b-PHEMA chain structures. Interestingly, the glass transition of DMP/PHEMA-containing copolymers was reduced with respect to the PMMA homopolymer. In addition, the thermal stability was enhanced with increasing DMP content in P(MMA-co-DMP) copolymers and was further enforced by incorporating PHEMA blocks. The presence of DMP/PHEMA segments should improve the thermal behavior of acrylic materials, which is of great interest in the design of versatile bone cements for total joint arthroplasty and functional coatings in targeted drug delivery.
Water near bioinert self-assembled monolayers Polym. J. (IF 2.17) Pub Date : 2018-06-06 Ryongsok Chang, Syifa Asatyas, Ganchimeg Lkhamsuren, Makoto Hirohara, Evan Angelo Quimada Mondarte, Kasinan Suthiwanich, Taito Sekine, Tomohiro Hayashi
For a long time, water has been speculated to play an essential role in the interactions of proteins and cells with artificial biocompatible materials. The current question is how water molecules at the interfaces affect the adsorption of proteins and the adhesion of cells. To answer this question, we introduce recent works that investigated the interfacial behavior of water near self-assembled monolayers (SAMs) by different types of analytical techniques. By combining these findings, we discuss how interfacial water affects the protein and cell resistance of various bioinert SAMs.
Butylated lignin as a compatibilizing agent for polypropylene-based carbon fiber-reinforced plastics Polym. J. (IF 2.17) Pub Date : 2018-06-06 Hiroki Sakai, Kosuke Kuroda, Takayuki Tsukegi, Tomoki Ogoshi, Kazuaki Ninomiya, Kenji Takahashi
Lignin is a renewable resource, but it is also considered a waste or a very-low-value material. Herein, we propose a lignin-derived compatibilizing agent as an alternative to the current compatibilizing agents. We prepared a polypropylene-based carbon fiber-reinforced plastic (CFRP) with butylated lignin (C4 lignin). Upon the addition of C4 lignin, the dispersion of carbon fiber into the matrix, and the adhesion between the carbon fiber and the matrix were greatly improved. As a result, the tensile strength of the CFRP prepared with C4 lignin was greater than that of the CFRP without lignan lignin (37.1 compared to 40.2 MPa). This value is close to that of CFRPs prepared with maleic anhydride-modified polypropylene (40.9 MPa), an existing compatibilizing agent. C4 lignin is a promising candidate for biomass-derived compatibilizing agents for polypropylene-based CFRPs.
Enhancement of the glass transition temperature of poly(methyl methacrylate) by salt Polym. J. (IF 2.17) Pub Date : 2018-06-05 Asae Ito, Panitha Phulkerd, Viknasvarri Ayerdurai, Mizuki Soga, Antoine Courtoux, Azusa Miyagawa, Masayuki Yamaguchi
We investigated the effects of two metal salts, lithium trifluoromethanesulfonate (LiCF3SO3) and lithium bromide (LiBr), on the glass transition temperature (Tg) of poly(methyl methacrylate) (PMMA). Both LiCF3SO3 and LiBr greatly enhanced the Tg of PMMA under dry conditions. However, once the sample films were exposed to humidity, the PMMA containing LiCF3SO3 absorbed a large amount of water, which acts as a plasticizer. As a result, the Tg shifted to a lower temperature, which limits the utility of this polymer in industrial applications. In contrast, the Tg of PMMA containing LiBr was minimally affected by the absorption of water. This phenomenon can be explained by the ion–dipole interactions with the small number of dissociated lithium cations.
Morphology and optoelectronic characteristics of organic field-effect transistors based on blends of polylactic acid and poly(3-hexylthiophene) Polym. J. (IF 2.17) Pub Date : 2018-06-05 Chia-Jung Cho, Shu-Yuan Chen, Chi-Ching Kuo, Loganathan Veeramuthu, Ai-Nhan Au-Duong, Yu-Cheng Chiu, Shang-Hung Chang
This study investigates the influence of the solvent used to prepare films of a poly(3-hexylthiophene) (P3HT) and poly(lactic acid) (PLA) blend on the morphology and charge transport mobility of field-effect transistors (FETs). Films prepared from CH2Cl2, a poor solvent for P3HT, tended to form well-defined nanowires, attributable to P3HT self-assembly via a solubility-induced process. This phenomenon resulted in a mobility of 5.30 × 10−3 cm2 (Vs)−1 and an on/off ratio of 3.23 × 103 in a CH2Cl2-solvent P3HT/PLA-blend system with a P3HT content of 10 wt%. Even a blend with 2 wt% P3HT exhibited a mobility of 1.76 × 10−3 cm2 (Vs)−1. However, in blend systems where CHCl3 solvent was employed in film preparation, the mobility decreased as the PLA content increased, and almost no electrical characteristics were exhibited at 50 wt% P3HT due to the isolated, spherical, phase-separated morphology of P3HT aggregation. Moreover, in CH2Cl2 solvent systems, the mobility of the P3HT/PLA (10/90) blend decreased from 5.3 × 10−3 cm2 (Vs)−1 (in a glove box) to 3.7 × 10−3 cm2 (Vs)−1 (after 28 days of air exposure), whereas that of 100 wt% P3HT declined by approximately one order of magnitude. These results confirm that P3HT/PLA blends prepared from CH2Cl2 solvent can be used to fabricate environmentally friendly, low-cost FETs with favorable air stability.
PJ ZEON Award for outstanding papers in Polymer Journal 2017 Polym. J. (IF 2.17) Pub Date : 2018-06-05 Takashi Kato
PJ ZEON Award for outstanding papers in Polymer Journal 2017 PJ ZEON Award for outstanding papers in Polymer Journal 2017, Published online: 05 June 2018; doi:10.1038/s41428-018-0048-4 PJ ZEON Award for outstanding papers in Polymer Journal 2017
Publisher Correction: Functional polymers in nonpolar solvents induced by dissociation of macromolecular complexes Polym. J. (IF 2.17) Pub Date : 2018-06-05 Kazuki Sada
Publisher Correction: Functional polymers in nonpolar solvents induced by dissociation of macromolecular complexes Publisher Correction: Functional polymers in nonpolar solvents induced by dissociation of macromolecular complexes, Published online: 05 June 2018; doi:10.1038/s41428-018-0063-5 Publisher Correction: Functional polymers in nonpolar solvents induced by dissociation of macromolecular complexes
Monodisperse engineered PEGs for bio-related applications Polym. J. (IF 2.17) Pub Date : 2018-06-01 Kazushi Kinbara
The importance of monodisperse poly(ethylene glycols) (PEGs) and their derivatives is rapidly increasing. Focusing on the merits of heterobifunctional PEGs, we developed a chromatography-free procedure for the preparation of monodisperse monotosylated PEGs. This technique enables the preparation of 8- to 16-mers in relatively large quantities, with good yields and purities, and facilitates the investigation of PEG-based functional molecules. For example, we synthesized structured PEGs consisting of monodisperse PEGs and polyols, which had specific two-dimensional shapes. These structured PEGs exhibited unique properties in aqueous environments; the triangular molecule dehydrated at a lower temperature than linear compounds with a similar molecular weight and could thus suppress the aggregation of proteins at high temperatures. We also found that the introduction of an aromatic group into the PEG skeleton lowered the dehydration temperature, which decreased the critical solution temperatures (LCSTs). Recent achievements in the development of engineered poly(ethylene glycol)s (PEGs) will be highlighted in this review.
Synthesis of polymers carrying adamantyl substituents in side chain Polym. J. (IF 2.17) Pub Date : 2018-06-01 Takashi Ishizone, Raita Goseki
This review addresses the synthesis of various polymers carrying bulky and rigid adamantyl substituents in their side chains. Synthetic methods for these polymers include typical polymer reactions of introducing adamantyl groups into existing polymers and the polymerization of monomers bearing pendant adamantyl groups. In particular, with regard to the latter synthetic method, the addition polymerization of adamantyl-containing vinyl monomers such as α-olefins, acetylenes, (meth)acrylates, (meth)acrylamides, vinyl ethers, 1,3-dienes, and styrenes is described. A variety of vinyl monomers are capable of undergoing living anionic polymerization to afford polymers with predictable molecular weights and narrow molecular weight distributions (M w/M n = 1.1). In several cases, the introduced adamantyl groups afford steric hindrance to prevent side reactions and control the addition modes of the polymerization. In general, the resulting adamantyl-substituted polymers show extremely high glass transition temperatures and high thermal stability derived from the stiff adamantyl substituents compared with the corresponding parent polymers.
Synthesis of sulfone-containing non-ionic polyurethanes for electrophoretic deposition coating Polym. J. (IF 2.17) Pub Date : 2018-06-01 Akinori Ohno, Mikihiro Hayashi, Akinori Takasu
The desire to develop a sustainable society has recently inspired polymer chemists to explore functional polyurethane materials because of their versatile material shape and thermoplasticity. To develop further functionalities of polyurethane materials and manipulation methods, here, we report the synthesis and a new method for coating non-ionic polyurethanes containing sulfonyl groups with utilizing electrophoretic deposition. The polyurethanes were synthesized via polyaddition of methylenediphenyl 4,4′-diisocyanate (MDI) with 2,2′-thiodiethanol in the absence or presence of triethylene glycol (TEG) as the soft ternary segment of the polymer, followed by oxone oxidation. The electrophoretic behaviors of the polyurethanes toward a stainless-steel electrode were investigated, and the peeling resistance and scratch resistance of a polyurethane film coated on a plate were evaluated by cross-cut adhesion and pencil hardness tests, respectively. These tests revealed that incorporation of soft TEG segments at an appropriate fraction can enhance both peeling resistance and scratch resistance. We also tested the enhancement in the transparency of the coated films, which do not lose their favorable peeling resistance and scratch resistance in the process, by replacing the aromatic diisocyanate component (MDI) with an alicyclic diisocyanate, dicyclohexylmethane 4,4′-diisocyanate (HMDI).
Design and application of redox polymers for nanomedicine Polym. J. (IF 2.17) Pub Date : 2018-05-23 Yukio Nagasaki
Reactive oxygen species (ROS), such as superoxide and hydroxyl radicals, cause oxidative stress that strongly affects aging and various diseases. Although various antioxidants have been developed to eliminate ROS, they cause serious problems by destroying important redox reactions in normal cells. We designed redox polymers with antioxidants covalently bonded to them. These polymers, with a self-assembling property, form nanoparticles in aqueous media (redox nanoparticles; RNPs), suppress uptake into normal cells, accumulate at inflammation sites, and effectively prevent ROS-related diseases. As such, RNPs have been found to be effective in preventing diseases involving ROS, such as myocardial and cerebral ischemia-reperfusion injuries, ulcerative colitis, and cancer. Redox polymers have several other applications. We designed redox injectable gels (RIGs), which transform from flowable solution at ambient temperature to gel at body temperature under the physiological conditions. RIGs can be applied for suppression of local inflammation, such as periodontitis. RIGs can also be used in anti-tissue adhesion sprays applied after physical surgery. Redox polymers can also be used as a surface coating of biodevices to make them blood compatible. This review summarizes the synthesis and application of these redox polymers.
Low-bandgap semiconducting polymers based on sulfur-containing phenacene-type molecules for transistor and solar cell applications Polym. J. (IF 2.17) Pub Date : 2018-05-23 Hiroki Mori, Yasushi Nishihara
The incorporation of a highly extended π-electron system into a polymer backbone is an effective strategy to develop high-performance donor–acceptor (D–A) polymers suitable for organic electronics because this strategy can facilitate a dense π-π stacking structure, leading to efficient carrier transport. With this in mind, we developed phenanthro[1,2-b:8,7-b′]dithiophene (PDT) because this new phenacene-type molecule has a highly crystalline nature, deep HOMO level, and high hole mobility, which are characteristics known to be suitable for a donor unit in high-performance D–A polymers. In this focus review, we report recent progress in PDT-containing D-A polymers combined with various strong acceptor units. Incorporation of PDT into a polymer backbone results in deep HOMO energy levels of −5.4~−5.5 eV, strong aggregation, and a dense packing structure with a short π-stacking distance of 3.5~3.6 Å. PDT-based polymers with appropriate alkyl side chains exhibit high hole mobilities of up to 0.18 cm2 V−1 s−1 in organic field-effect transistor (OFET) devices due to their tendency to form highly ordered edge-on structures. Furthermore, we can adjust their level of molecular orientation from edge-on to face-on by increasing their molecular weight, leading to a high power conversion efficiency of over 6% in polymer solar cell (PSC) applications. These results demonstrate that PDT is a good candidate as a high-performance building block in D-A polymers.
Synthesis and thermal properties of poly(oligomethylene-cycloalkylene)s with regulated regio- and stereochemistry Polym. J. (IF 2.17) Pub Date : 2018-05-22 Daisuke Takeuchi
This article focuses on the synthesis and thermal properties of poly(oligomethylene-cyclopentylene)s and poly(oligomethylene-cyclohexylene)s with regulated regio- and stereochemistry. Pd complexes with diimine ligands promote controlled isomerization polymerization of 4-alkylcyclopentenes to afford polymers with 1,3-trans-cyclopentylene groups and oligomethylene spacers alternating along the polymer chain. Pd complexes with a C2 symmetric structure enable isospecific polymerization of 4-alkylcyclopentenes, and the resultant isotactic polymers show liquid-crystalline properties. Cyclopolymerization of 1,6-heptadiene by bis(imino)pyridine Fe and Co catalysts produces poly(ethylene-1,2-cyclopentylene) with cis and trans-stereochemistry, respectively. Synthesis of poly(oligomethylene-1,4-cyclohexylene)s with trans or cis structure can be achieved by Pd-catalyzed isomerization polymerization of alkenylcyclohexanes or methylenecyclohexanes. The polymers with 1,4-trans-cyclohexylene show a high melting point that depends on the length of the oligomethylene spacer in the polymer. The thermal properties of the poly(oligomethylene-cyclopentylene)s and poly(oligomethylene-cyclohexylene)s are compared to those of previously reported polymers with different regio- or stereochemistry.
Application of a polarized modulation technique in supramolecular science: chiroptical measurements of optically anisotropic systems Polym. J. (IF 2.17) Pub Date : 2018-05-21 Takunori Harada
The chirality of a supramolecular assembly provides particularly valuable information because the bonding nature of noncovalent interactions, such as electrostatic interactions, π effects, van der Waals forces, and hydrophobic effects, makes the development of supramolecular assemblies an attractive and useful approach in chiral induction, chiral amplification, and chirality transfer. However, chiroptical measurements of optically anisotropic samples cannot be generally achieved with modern chiroptical spectrophotometric methods such as circular dichroism (CD) or circular birefringence (CB) and circularly polarized luminescence (CPL) that are based on polarization modulation techniques because of the coupling effect of the nonideal optics and the electronics with strong macroscopic anisotropies, that is, nonchiral signals related to linearly polarized phenomena. These artifact signals are often much stronger than the chiroptical signals. Only CD and CPL spectrophotometers developed in 2001 and 2016, respectively, and integrated into a Stokes–Mueller matrix analysis for optically anisotropic samples are capable of obtaining accurate chirality measurements of samples with macroscopic anisotropies. Therefore, these spectrophotometers enable chiral investigations of optically anisotropic samples, for example, single crystals, supramolecular assemblies, gels, films, membranes, polymers, and liquid crystals. This focus review presents a short and elementary discussion of the chiroptical measurement techniques for optically anisotropic samples in supramolecular science and signal interpretation in polarization spectroscopy.
Nucleation effects of high molecular weight polymer additives on low molecular weight gels Polym. J. (IF 2.17) Pub Date : 2018-05-21 Symone L. M. Alexander, LaShanda T. J. Korley
Polymeric species have been introduced to low molecular weight gelators to tailor their nucleation and rheological behavior. This work combines polymers and molecular gels (MGs) in a different manner by using polymers as the major component in a solution. Additionally, using polymers above their entanglement molecular weight is a step towards building polymer–MG composite materials. Specifically, a cholesterol-pyridine (CP) molecular gel was introduced to poly(ethylene oxide-co-epichlorohydrin) (EO-EPI) and poly(vinyl acetate) (PVAc), which have dissimilar chain conformations in anisole. Dynamic light scattering, scanning electron microscopy, and temperature-dependent small- and wide-angle X-ray studies were utilized to investigate the influence of the solution properties of high molecular weight EO-EPI and PVAc on the CP network structure. The collapsed chain conformation and aggregation of EO-EPI led to isolated, branched CP fiber networks, resulting in unexpectedly high dissociation temperatures. In contrast, PVAc gels displayed transient fiber networks, as evidenced by fiber wrapping and bundling. Cooperative interactions between PVAc and CP resulted in gels with dissociation temperatures higher than those of pure CP gels. These structural characteristics significantly influenced the gel mechanics. The collapsed chain conformation of EO-EPI led to weaker, more viscous gels, and the freely extended PVAc chain conformation led to interconnected, elastic gels independent of the molecular gel concentration.
Photochemical liquefaction and softening in molecular materials, polymers, and related compounds Polym. J. (IF 2.17) Pub Date : 2018-05-21 Takahiro Yamamoto, Yasuo Norikane, Haruhisa Akiyama
Recent developments in materials showing photo-induced liquefaction and softening, including molecular materials, gels, and polymers, are described. A macrocyclic azobenzene molecule that has long alkoxy chains was first reported to show a photo-induced solid–liquid phase transition at room temperature through trans–cis photoisomerization. The structure–property relationship for understanding the photo-induced phase transition has since been investigated by using model compounds with a simple molecular design. Such azobenzene-based materials also exhibited dynamic motion on glass and water surfaces; these motions are driven by continuous liquefaction/crystallization and dissolution of the liquefied material. Photo-induced liquefaction has been further developed in middle molecular and polymeric materials. The effects of the alkyl chain length, functional groups, and number of azobenzene units on the photo-induced behavior have been extensively investigated. In addition, by using photoresponsive gelators, the photo-induced quasi-solid–liquid (gel–sol) phase transition of gels was accomplished. Moreover, very recently, a photoresponsive plasticizer that can plasticize “photo-inactive” polymers by light irradiation has been proposed.
Fracture processes of crystalline polymers using coarse-grained molecular dynamics simulations Polym. J. (IF 2.17) Pub Date : 2018-05-21 Yuji Higuchi
Molecular simulations are powerful tools for revealing the properties of polymers at the molecular level. In particular, coarse-grained molecular dynamics simulations are useful for elucidating the deformation and fracture processes of polymers. However, in the case of crystalline polymers, it is difficult to reproduce experimentally observed structures and mechanical properties using these models. This review describes our recent investigations into the deformation and fracture processes of crystalline polymers using coarse-grained molecular dynamics simulations. We were able to successfully reproduce the lamellar structure of polyethylene, which is a fundamental structural feature of this polymer, and obtain a stress–strain curve that exhibited good consistency with that observed experimentally. The molecular dynamics simulations revealed that void generation in the amorphous layers was caused by the movement of the chain ends, which is difficult to observe through experiments. The conditions required to reproduce the experimentally observed structure and mechanical properties using molecular simulations are also discussed.
Development of macromolecules and supramolecules based on silicon and arsenic chemistries Polym. J. (IF 2.17) Pub Date : 2018-05-21 Hiroaki Imoto
Organic–inorganic hybrids are one of the most important tools in materials science. Since the incorporation of abundant elements into single molecules realizes molecular-level hybridization, organic–inorganic hybrid molecules and polymers have attracted increasing attention. In this focus review, the author’s recent works on hybrid materials utilizing silicon and arsenic are overviewed. Among widely used silicon compounds, silsesquioxane ((RSiO1.5) n ), adopting a cage structure, is a key structure. Polyhedral oligomeric silsesquioxane (POSS) has been employed for the reinforcement of organic materials, but the author has been working on “single-molecular POSS materials” and “main-chain-type POSS polymers.” In the last half of this review, organoarsenic polymers and supramolecules are introduced. Though experimental studies on organoarsenic compounds have been avoided due to the dangers of conventional synthetic procedures, the author’s practical methods have strongly contributed to the syntheses of functional organoarsenic compounds. The high functionality and usability of organoarsenic compounds are demonstrated.
Conjugation break spacers and flexible linkers as tools to engineer the properties of semiconducting polymers Polym. J. (IF 2.17) Pub Date : 2018-05-18 Aiman Rahmanudin, Liang Yao, Kevin Sivula
Developing tools to understand and control the effect of semiconducting polymer morphology on the optoelectronic performance remains an important objective. Introducing conjugation break spacers (i.e., flexible linkers) between π-conjugated segments in a semiconducting polymer is an emerging strategy toward this goal. Herein, we place this strategy in context with other extrinsic and intrinsic engineering approaches and highlight some of the recent results employing this “flexible linker” approach. We see that the inclusion of electrically insulating aliphatic spacers represents a versatile tool to gain insight into the nature of inter-molecular and intra-molecular charge carrier transport and can be broadly used to control morphology of solution-processed semiconducting polymer thin films. Moreover, this approach has afforded unique control over material processing and mechanical properties (e.g., viscosity and elasticity) without detrimental effect on the semiconducting ability. While the development of this technique remains at an early stage, its potential gives promise to reaching the goal of engineering the self-assembly of semiconducting polymers.
Synthesis and properties of hyperbranched polymers by polymerization of an AB3-type incompletely condensed cage silsesquioxane (IC-POSS) monomer Polym. J. (IF 2.17) Pub Date : 2018-05-18 Sota Yuasa, Hiroaki Imoto, Kensuke Naka
An incompletely condensed cage silsesquioxane (IC-POSS)-based AB3-type monomer, tris(dimethylsilyl)-p-vinylhexaisobutyl-IC-POSS (3), was prepared by the corner-cleaved reaction of vinylheptaisobutyl-POSS (1) and subsequent capping reaction with chlorodimethylsilane. The structure of 3 was confirmed by FT-IR; 1H-, 13C-, and 29Si-NMR; and HR-FAB-MS analyses. These analyses also suggested 12.5 mol% contamination of tris(dimethylsilyl)-heptaisobutyl-IC-POSS (4). The hydrosilylation polymerization of 3 as an AB3-type IC-POSS monomer in the presence of Karstedt’s catalyst in toluene at 80 °C overnight provided a soluble polymer with a number average molecular weight (Mn) and molecular weight distribution (Mw/Mn) of the polymer that are 3.9 × 103 and 1.39, respectively. The resulting hyperbranched polymer (HB) reacted with two molar equivalents of isoprenol or allylheptaisobutyl-POSS against the Si–H groups in the presence of Karstedt’s catalyst in toluene at 80 °C for 7 h. The HB polymers before and after post functionalization with isoprenol or allylheptaisobutyl-POSS showed 1% weight loss at 298, 285, and 358 °C, respectively, under N2. Introducing POSS units at the terminus significantly increased the thermal stability. The XRD pattern of the HB polymers showed a denser structure formed in the allylheptaisobutyl-POSS-terminated HB polymer. The refractive index of the HB polymer before post functionalization was 1.4376. Post functionalization with isoprenol and allylheptaisobutyl-POSS increased the refractive index to 1.4464 and 1.4573, respectively.
Open-shell organic semiconductors: an emerging class of materials with novel properties Polym. J. (IF 2.17) Pub Date : 2018-05-18 Yiming Huang, Eilaf Egap
Organic materials with unpaired electrons along with the discovery of their unique properties have fascinated scientists for over a century. The development of open-shell molecules has recently been rekindled as the result of improved synthetic strategies and spectroscopic techniques. In this focus review, we provide an overview of open-shell polymers and small-molecules organic semiconductors. We review strategies toward molecular magnets or spin-polarized magnetic organic semiconductors that encompasses incorporation of stable radical groups directly into the backbone of organic semiconductors or preparing highly conjugated ladder-type molecules based on open–shell Kekulé–type structures to enable efficient spin delocalization along the conjugation length. These novel materials have the potential to make significant societal impacts in the areas of information, energy and human health technologies.
π-Conjugated polymer nanowires: advances and perspectives toward effective commercial implementation Polym. J. (IF 2.17) Pub Date : 2018-05-16 Wesley K. Tatum, Christine K. Luscombe
π-Conjugated polymers have continued to demonstrate their relevance and ability to be used in next-generation electronic and optoelectronic devices. Nanowires formed from semiconducting polymers can be easily produced and aligned, which considerably enhances the polymer’s properties, such as charge transport. This review discusses recent advances in the formation and alignment of semiconducting polymer nanowires. This includes whisker growth and self-assembly methods, as well as methods of nanoscopic confinement through composites and blends. Next, this review explores how semiconducting polymer nanowires have been successfully implemented in field-effect devices, sensors, and thermoelectrics.
Photoluminescence behavior of liquid-crystalline gold(I) complexes with a siloxane group controlled by molecular aggregate structures in condensed phases Polym. J. (IF 2.17) Pub Date : 2018-05-11 Kaori Fujisawa, Fumika Mitsuhashi, Preeyanuch Anukul, Kensuke Taneki, Osama Younis, Osamu Tsutsumi
Liquid-crystalline (LC) Au complexes with siloxane groups at the termini of flexible chains were synthesized. The effects of the molecular and molecular aggregate structures on the luminescence behavior of the complexes were investigated. All complexes used in this study showed LC phases. No direct effect of the siloxane group on the luminescence behavior of the complexes in solution was observed. However, in condensed phases, different luminescence colors were observed depending on the aggregate structure due to the effect of intermolecular interactions. Thus, the luminescence color of the Au complexes can be controlled by the intermolecular interactions based on the structure of the molecular aggregates. The complex with the siloxane group developed in this study showed two different luminescence colors, which can be controlled by changing the aggregate structures induced by the phase transition.
Self-assembly of liquid-crystalline block copolymers in thin films: control of microdomain orientation Polym. J. (IF 2.17) Pub Date : 2018-05-10 Xiaoxiong Zheng, Yongbin Zhao, Aihua Chen
Block copolymer (BCP) lithography, as one of the most promising techniques for the next-generation integrated circuits, has been extensively investigated in recent years. Among the diverse types of BCPs, liquid-crystalline BCPs (LC-BCPs) formed by incorporating LC moieties into the BCPs have become increasingly attractive because of the tunable alignment of the LC chains. This review highlights the control of the microdomain orientation of PEO-b-PMA(Az) thin films via novel and convenient processing methods, including micropore extrusion and the introduction of polydimethylsiloxane (PDMS). Meanwhile, the mechanisms of the microdomain alignment transition are clarified and are closely related to the soft shearing field and the change in the block surface energy. Furthermore, some new perspectives for future research on the self-assembly of LC-BCP thin films are outlined from the point of view of material design, orientation control, and technological innovation.
Self-assembled oligosaccharide-based block copolymers as charge-storage materials for memory devices Polym. J. (IF 2.17) Pub Date : 2018-05-08 Ai-Nhan Au-Duong, Chi-Ching Kuo, Yu-Cheng Chiu
Over the past few years, extremely high charge-storage capacities of glucose-based oligo- or polysaccharides have been discovered that enables such materials to hold a great potential in electronics applications due to their abundant and renewable materials. Typically, the introduction of an α-glucan-containing polysaccharide into the dielectric layer of a transistor-type memory device causes excellent irreversible electron-capture properties; hence, a transistor device embedded with oligosaccharide maltoheptaose domains expresses write-once-read-many (WORM)-type behavior, which confirms that green materials can be used for advanced electronics. However, their irreversible WORM-type characteristics also restrict the application α-glucan-containing polysaccharides in high-performance electronic devices. Recent advances in oligosaccharide-based block copolymers through the inherent immiscibility of different polymer segments can enhance not only the formation of self-assembled nanostructures but also the switching of memory properties. Furthermore, supramolecular structures composed of oligosaccharide-based block copolymers and conjugated moieties can be developed into high-performance nonvolatile organic field-effect transistor (OFET) memory devices. This mini review presents an overview of the recent literature in oligosaccharide maltoheptaose-based block copolymers and their promising applications in organic memory devices.
Design and synthesis of PEGylated amphiphilic block oligomers as membrane anchors for stable binding to lipid bilayer membranes Polym. J. (IF 2.17) Pub Date : 2018-05-07 Daiki Takahashi, Yuta Koda, Yoshihiro Sasaki, Kazunari Akiyoshi
Cell surface engineering is a potentially powerful method for manipulating living cells by decorating the cell membrane with specific molecules. Possible applications include cell therapy, drug delivery systems, bio-imaging, and tissue engineering. The stable binding of synthetic molecules to serve as artificial membrane protein anchors is a promising approach for appending functional molecules to the cell surface. However, such synthetic molecules have previously shown limitations, including cytotoxicity and low cell surface affinity. We synthesized amphiphilic block oligomers, using ruthenium-catalyzed living radical polymerization, as novel membrane anchors for stable binding to lipid bilayer membranes. AB and ABA-type amphiphilic block oligomers were synthesized with poly(ethylene glycol) methacrylate (PEGMA) and varying butyl methacrylate (BMA) contents (PEGMA/BMA ratios of 25/5–25/50). These PEGylated oligomers showed high binding efficiencies (up to 92%) for liposomes, which served as model cell membranes, and low cytotoxicity in K562 cells. Both the BMA content and the block segment sequence in the copolymers strongly affected their binding efficiencies. Oligomers with an ABA-type block structure were much more effective than AB-type block oligomers, random oligomers, or PEGMA homo-oligomers for stable membrane binding. Thus, precise control of the primary structures of the amphiphilic oligomers enabled tuning of their binding efficiencies. These amphiphilic block oligomers hold promise as novel membrane anchors in many biomedical applications.
Unpolarized light-induced alignment of azobenzene by scanning wave photopolymerization Polym. J. (IF 2.17) Pub Date : 2018-05-07 Miho Aizawa, Kyohei Hisano, Masaki Ishizu, Norihisa Akamatsu, Christopher J. Barrett, Atsushi Shishido
Controlling the alignment of various functional molecules is important for the development of many next-generation, high-performance optical devices. However, there are some limitations in inducing molecular alignment using the current methods. We report herein the alignment control of azobenzene in a polymer film by a simple, new alignment-patterning technique based on a scanning wave photopolymerization (SWaP) concept. In this technique, molecular alignment was induced by the spatiotemporal control of the non-polarized light. A photoisomerizable azobenzene molecule, Disperse Red 1 (DR1), was doped into the photopolymerizable mixture, and it was successfully aligned along the direction of the neighboring mesogens; the alignment was induced by SWaP with unpolarized light. The alignment behavior showed that the degree of photoisomerization of the doped azobenzene moieties was proportional to the light intensity, and the unidirectional alignment of DR1 was achieved through optimization of the photopolymerization conditions. This finding indicates that SWaP could be employed as a novel and simple fabrication process for preparing a wide variety of highly functional optical devices requiring alignment control.
Nanoribbon network formation of enzymatically synthesized cellulose oligomers through dispersion stabilization of precursor particles Polym. J. (IF 2.17) Pub Date : 2018-05-07 Takeshi Serizawa, Yuka Fukaya, Toshiki Sawada
Nanoribbon network formation of enzymatically synthesized cellulose oligomers through dispersion stabilization of precursor particles Nanoribbon network formation of enzymatically synthesized cellulose oligomers through dispersion stabilization of precursor particles, Published online: 07 May 2018; doi:10.1038/s41428-018-0057-3 Cellulose oligomers were synthesized via cellodextrin phosphorylase-catalyzed reactions using α-D-glucose 1-phosphate monomers and D-glucose primers. The products prepared at relatively high primer concentrations self-assembled into highly grown nanoribbon network structures. The nanoribbons were composed of cellulose oligomers with degree-of-polymerization (DP) values of 8-9 with certain degrees of DP distribution and displayed the cellulose II allomorph. A formation mechanism for the unique nanostructures was proposed based on analyses of reaction time-dependent differences of the product solutions.
A supramolecular thermocell consisting of ferrocenecarboxylate and β-cyclodextrin that has a negative Seebeck coefficient Polym. J. (IF 2.17) Pub Date : 2018-05-01 Teppei Yamada, Xiaopeng Zou, Yimin Liang, Nobuo Kimizuka
A p-type supramolecular thermocell was constructed with a ferrocenecarboxylate/ferroceniumcarboxylate pair. The Seebeck coefficient of the cell was improved from −0.86 to −1.20 mV K−1 by the addition of β-cyclodextrin. Isothermal titration calorimetry and a theoretical investigation demonstrated that the host–guest interaction increased the Seebeck coefficient.
Apatite coating on dendrimer-modified buckypaper and the formation of nanoapatite on MWCNTs Polym. J. (IF 2.17) Pub Date : 2018-05-01 Tomoyuki Tajima, Tomoaki Tanaka, Hideaki Miyake, Ill Yong Kim, Chikara Ohtsuki, Yutaka Takaguchi
Multi-walled carbon nanotube (MWCNT)/dendrimer sheet scaffolds, i.e., dendrimers attached to the surface of MWCNT buckypaper, were fabricated, and a hydroxyapatite (HAp) coating prepared on dendrimer-modified buckypaper using an alternate soaking process (ASP) is described. The amount of the HAp that is retained on the surface of the MWCNT/dendrimer sheet scaffolds depends on the modification method; i.e., surface modification performed after the formation of the buckypaper is much more effective in producing MWCNT/HAp hybrid materials than surface modification prior to the formation of the buckypaper. Moreover, biomimetic crystallization of calcium phosphate on buckypaper in simulated body fluid (SBF) was carried out. TEM analysis of the resulting MWCNT/dendrimer sheet scaffolds revealed that the MWCNT backbone was covered with scaly crystals.
Water-insoluble, nanocrystalline, and hydrogel fibrillar scaffolds for biomedical applications Polym. J. (IF 2.17) Pub Date : 2018-04-26 Dong-Hee Kang, Dongyoon Kim, Sungrok Wang, Dasom Song, Myung-Han Yoon
Recently, micro/nanofibrillar materials have been widely utilized for a variety of applications in many different fields of research due to their relatively large surface-to-volume ratios, high porosity, and three-dimensional connectivity, along with their cost-effective fabrication processes. Herein, we present a review of recent progress in the development of micro/nanofibrillar scaffolds with a specific focus on their biomedical applications. From the perspective of controlling polymer–polymer and polymer–water molecular interactions, we categorized the fibrillar scaffolds into insoluble, nanocrystalline, and hydrogel fibers. Based on our recent studies related to this research topic, we provide the significance and essential information on four different micro/nanofibrillar scaffolds: (1) solid micro/nanofibrillar scaffolds based on water-insoluble polymers, (2) hydrogel nanofibrillar network scaffolds based on crystalline bacterial cellulose, (3) hydrogel micro/nanofiber scaffolds based on partially precipitated PVA, and (4) hydrogel micro/nanofiber scaffolds based on chemically cross-linked PVA. The present discussion should provide guidance to researchers in selecting a micro/nanofibrillar scaffold suitable for their own purposes and should help inspire them to develop more sophisticated fibrillar scaffolds in the future.
Microanalysis using surface modification and biphasic droplets Polym. J. (IF 2.17) Pub Date : 2018-04-25 Taisuke Kojima, Shuichi Takayama
Conventional methods for the synthesis and analysis of chemical and biological materials often utilize homogeneous bulk environments or surface immobilization on a substrate. Homogeneous bulk environments, however, require large quantities of samples and reagents as well as significant effort to functionalize materials. Liquid–substrate interfaces can also pose problems because adsorption can hinder diffusion and reagent transport during bioanalyses, and sensitive materials, such as proteins, experience denaturation, or other types of deformation. Here, we describe the construction and use of droplet microenvironments created through a combination of surface modification, water-in-oil systems, and aqueous two-phase systems (ATPSs). This integration of an immobilization-free droplet microenvironment with liquid–liquid interfaces, material compartmentalization, directional reagent transport, and small volumes enables unique material functions. Specific examples include ATPS-assisted fabrication of functional microparticles for drug delivery, microscale determination of ATPS phase diagrams, dendritic self-assembly of semiconductive nanoparticles, multiplex immunoassays, and analysis of breast cancer cell migration.
Advances in surface-coated single-walled carbon nanotubes as near-infrared photoluminescence emitters for single-particle tracking applications in biological environments Polym. J. (IF 2.17) Pub Date : 2018-04-24 Zhenghong Gao
Single-particle tracking (SPT) represents a powerful tool for revealing the single-molecule dynamics in a number of biological processes in live cells and biological tissue. Single-walled carbon nanotubes (SWCNTs) are promising photoluminescence emitters for SPT applications in various biological environments due to their characteristic large-aspect-ratio structures along with their bright and stable near-infrared (NIR) photoluminescence, which are invaluable for long-term video-rate imaging and tracking applications at the single-molecule level with high signal-to-noise ratios (SNRs). Recent advances in applying SWCNTs as NIR photoluminescence emitters have highlighted the understanding of brain tissue organization at the nanometer scale. In the first section, this review article summarizes the latest advances in different surface coatings commonly used for encapsulating SWCNT surfaces via molecular self-assembly in order to obtain surface-coated nanotubes with low cytotoxicity and minimal nonspecific interactions with live cells while maintaining their emission of bright photoluminescence to enable long-term photoluminescent imaging and tracking at the single-nanotube level in biological environments. The second section offers a comparison of different excitation strategies of (6,5) SWCNTs to determine the best excitation wavelength for efficient video-rate imaging and tracking of individual nanotubes in live brain tissue for up to tens of minutes without inducing unacceptable phototoxicity or temperature increases. Finally, this review showcases that, by utilizing the photoluminescence tracking of single nanotubes combined with super-resolution single-molecule localization microscopy technologies, it is practical to elucidate the ultrafine nanometer-scale organization of the brain extracellular space (ECS) and probe the local rheological properties of young rat brain with a subdiffraction optical resolution down to 50 nm at a subwavelength accuracy of ~40 nm. The findings primarily indicate the great diversity of the brain ECS and the inhomogeneous properties of the local viscosity in live brain tissue. Overall, because of their advantages of low cytotoxicity, bright photoluminescence, high SNRs (~25), and deep tissue penetration (~100 μm) for long-term video-rate imaging and tracking at the single-nanotube level under 845 nm excitation (K-momentum exciton–phonon sideband, KSB), phospholipid-polyethylene glycol-coated SWCNTs hold great potential as NIR photoluminescence emitters for single-particle tracking in biological environments, as exemplified here in live brain tissue, and may find extended applications in elucidating the fundamental roles of the brain ECS in various biological processes, such as sleep, memory, aging, brain tumor progression, and neurodegenerative disease development.
Highly sensitive and rapid biosensing on a three-dimensional polymer platform Polym. J. (IF 2.17) Pub Date : 2018-04-20 Madoka Takai
Increasing sensitivity and decreasing assay time are two of the most crucial goals in the development of biosensing devices, such as immunoassays, protein electrophoresis, and bioimaging nanoprobes. We have developed three-dimensional (3D) nano/microstructured platforms for biosensing devices aimed at highly sensitive and rapid immunoassays. One such platform is a nanosphere structure with poly[2-methacryloyloxyethyl phosphorylcholine-co-n-butyl methacrylate-co-p-nitrophenyloxycarbonyl poly(ethylene glycol) methacrylate] (PMBN) prepared by the electrospray deposition (ESD) method. Compared with flat PMBN, the 3D nanosphere surface enables the immobilization of a large amount of antibody to enhance the specific signal of the immunoassay. Furthermore, PMBN is resistant to non-specific protein adsorption. Thus, this 3D nanosphere structure can be applied in microchip environments, leading to highly sensitive and rapid immunoassays. To obtain a more rapid assay that takes at most 5 min, we utilized another platform: a 3D polystyrene (PS) microfiber structure prepared by ESD paired with vacuum pump pressurization to induce bulk flow. This system takes advantage of the increased amount of antibody immobilized on the 3D microfiber and the accelerated propagation of antigens through the microfiber induced by the vacuum pump to enable an efficient and rapid immunoassay.
Liquid-crystalline behavior and ion transport properties of block-structured molecules containing a perfluorinated ethylene oxide moiety complexed with a lithium salt Polym. J. (IF 2.17) Pub Date : 2018-04-18 Taira Onuma, Masafumi Yoshio, Masaki Obi, Kimiaki Kashiwagi, Shinya Tahara, Takashi Kato
The liquid-crystalline behavior of fluorinated block-structured molecules and the ion transport properties of their complexes with a Li salt have been examined. The block-structured molecules comprise a perfluorinated oligo (ethylene oxide) moiety containing a terminal methyl carbonate or a terminal hydroxyl group and an octadecyl moiety. These molecules exhibit highly ordered smectic phases. The fluorinated molecule with a terminal methyl carbonate possesses an isotropization temperature lower than that of the analogous non-fluorinated molecule. The fluorinated molecule complexed with a Li salt shows ionic conductivities on the order of 10−6 S cm−1 in the smectic phase formed at ambient temperature, while conductivities on the order of 10−5 S cm−1 are observed in the isotropic phase.
Preparation of nano- and microstructures through molecular assembly of cyclic oligosaccharides Polym. J. (IF 2.17) Pub Date : 2018-04-17 Hajime Shigemitsu, Toshiyuki Kida
The shape, size, and size distribution of nano- and microstructures formed by the self-assembly of small molecules are crucial factors that govern their chemical and physical properties. Understanding these factors can reveal the correlations between the supramolecular structure and the emergent properties and may realize innovative new materials. Hence, the formation processes and syntheses of nano- and microstructures consisting of various functional molecules have been actively studied. Herein, we report the bottom-up preparation and functions of nano- and microstructures formed by the self-assembly of cyclodextrins (CDs), which are cyclic oligosaccharides. Reprecipitation and electrospinning methods produce various supramolecular structures based on CDs. The assembly modes of CD molecules and their morphologies remarkably affect the properties and functions of the supramolecular structures. In particular, γ-CD-based supramolecular structures achieve the inclusion of guest molecules dissolved in oils, which is difficult to achieve with a single-CD molecule. Furthermore, cubic γ-CD structures show excellent dispersibility in oils, forming organogels in various oils, and organic solvents at ambient temperature. These studies indicate that the construction and morphological control of self-assembled CD structures can effectively realize the potential function of CD molecules and open new fields in oligosaccharide chemistry and supramolecular chemistry.
Mesomorphic glass-forming ionic complexes composed of a cholesterol phthalate and 1-Cn-3-methylimidazolium: phase transition and enthalpy relaxation behavior Polym. J. (IF 2.17) Pub Date : 2018-04-12 Itaru Nakajima, Taishi Kitaguchi, Kazuki Sugimura, Yoshikuni Teramoto, Yoshiyuki Nishio
Ionic complexes consisting of a mesogenic cholesterol derivative and 1-alkyl (Cn)-3-methylimidazolium (CnMim) (n = 6–18) were prepared from ethanol solutions containing an equimolar mixture of cholesterol hydrogen phthalate (CHP) and 1-Cn-3-methylimidazolium hydroxide; the imidazolium hydroxide was obtained by anion exchange of 1-Cn-3-methylimidazolium bromide. The complex samples, termed [CnMim][CHP], were examined to evaluate their thermal transition patterns. Excluding the two samples (n = 6, 8) that showed no definite ordered phase, the complexes with n ≥ 10 formed a cholesteric (n = 10, 12) or smectic (n = 14–18) mesophase in a considerably wide range of temperatures; this wide range reflects the additional thermotropic property of the salts of CnMim with longer alkyl chains. These fluid mesophases transformed into a mesomorphic vitreous solid without crystallization in a usual cooling process. For the glassy mesomorphic samples of selected complexes (n = 10, 18), the enthalpy relaxation behavior was followed as a function of the aging temperature and time, and the data were analyzed in terms of a Kohlrausch–Williams–Watts (KWW) type of stretched exponential equation. A very narrow distribution of relaxation times was observed for the “liquid crystalline glasses”, indicating the high uniformity of the relaxation mode.
Direct arylation polycondensation as conjugated polymer synthesis methodology Polym. J. (IF 2.17) Pub Date : 2018-04-09 Kazuhiro Nakabayashi
Direct arylation polymerization (DArP), which is a cross-coupling polymerization between a dihaloarene monomer and a non-substituted arene monomer, has attracted widespread attention for conjugated polymer synthesis. In DArP, no prior preparation of arene monomers with organometallic functionalities is necessary, in contrast to typical cross-coupling polymerizations such as the Suzuki and Stille reactions. Furthermore, the low toxicity of the byproducts of DArP contributes to green chemistry. In terms of efficiency and environmental friendliness, these advantages make DArP an attractive next-generation polymer synthetic method. To date, numerous conjugated polymers have been synthesized by DArP. However, many problems remain to be overcome, including better understanding of the correlation between polymer structure and DArP factors, the design of a more efficient DArP system, and so on. Addressing these problems could lead to the establishment of DArP as a viable alternative for conjugated polymer synthesis. We revealed that a variety of conjugated polymers such as donor–acceptor alternating copolymers (arylene diimide-based donor–acceptor alternating copolymers and thienoisoindigo-based donor-acceptor alternating copolymers) and regioregular poly(3-alkylselenophene)s were successfully synthesized by the DArP strategy based on appropriate molecular design and adjustment of the catalytic system. This focus review will describe our recent studies developing the synthesis of novel conjugated polymers via DArP.
Some contents have been Reproduced by permission of The Royal Society of Chemistry.
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