Articles in 2016

This report reviews the seminal features and characteristics of free-standing polymeric ultrathin films (nanosheets), including fabrication methods, mechanical properties and biomedical and health-care applications (for example, wound dressings, tissue engineering materials and bioelectronic devices). ‘Nanosheet technology’ is a promising approach for the development of advanced medical applications and health-care practices in surgery and regenerative medicine, as well as for connecting the human body to electronic interfaces for future medical applications.

This review focused on the various polymers composed of trimethylene carbonate (TMC) units and ethylene glycol (EG) units. Poly(TMC) is a biodegradable polymer that is used in biomedical materials. It has been reported that its combination with oligo(EG) and poly(EG) would offer a useful approach. In addition, monomer design and polymer reactions are available. These polymers, including TMC and EG units, are useful in preparing various nanostructures and they have the potential for application in biomedical materials.

Polyimide aerogel (PIA) was used to synthesize low-dielectric-constant polyimide composite films. Unlike silica aerogel composites, the polyimide aerogel composite films were synthesized solely based on polyimide. The films maintained the original thermal and chemical properties of polyimide contributing to their homogeneity. The presence of uniformly dispersed aerogel, the high-thermal decomposition and glass transition temperature of the PI–PIA sample films were confirmed by field emission scanning electron microscope, TGA and DSC analysis. The FE-SEM image of the PI–PIA film samples indicates that the PIA particles were well-dispersed in the film and retained their spherical shape.

Novel polymeric metal complex dyes with phenothiazine or carbazole derivative as donor and Zn(II) or Co(II) complexes as acceptors were synthesized for dye-sensitized solar cells. The dyes based on carbazole derivatives exhibited wider absorption spectra, and after replacement of the Co(II) coordinated ion with Zn(II), a bathochromic shift in the absorption spectrum was observed. The device sensitized by P3 exhibited the best photocurrent conversion efficiency (2.06%). Moreover, these dyes all exhibited excellent chemical and thermal stability.

Microrod patterns were fabricated on PDMS sheets utilizing porous silicon wafers as templates. The prepared microrod PDMS surface showed high water and oil contact angles. To discuss the mechanism, theoretical contact angles were calculated utilizing Wenzel model and Cassie-Baxter model, and compared with the measured values. Furthermore, it was confirmed that the microrod PDMS surface has self-cleaning property.

The antigen-loaded liposomes modified with pH-sensitive polymers and adjuvants were taken up by dendritic cells and induced fusion with endosomal membranes, responding to the acidic pH inside of the endosomes, thus causing the transfer of the antigen into the cytosol, as shown in the fluorescence microscopic image (green: fluorescein isothiocyanate-labeled antigen, red: liposome). As a result, cross-presentation is promoted, leading to the induction of cellular immunity. In addition, the dendritic cells are activated by adjuvants, which causes the activation of cellular immunity, resulting in therapeutic effects on tumor-bearing mice.

Optically active polyurethane (OPU) derived from chiral tyrosine possesses a single-handed helical conformation and optical activity owing to the induced asymmetric force field in the chiral monomer. The regular secondary structure facilitates the formation of numerous interchain hydrogen bonds, which increases the crystallinity and thermal stability of OPU. The high-temperature infrared spectroscopy results indicate that the hydrogen bonding collapses before thermal decomposition. Both helical stereostructures and hydrogen bonding contribute to the decreasing of infrared emissivity for OPU.

Amorphous and flexible tri-branched poly(ricinoleic acid) was introduced to semi-crystalline and rigid trans-1,4-polyisoprene from Eucommia ulmoides Oliver to improve the processing ability.

Specific hydrolysis properties of microbial copolyester P(3HB-co-6%-3HHx) was found during super-heated steam treatment in a temperature range of 130–190 °C. From changes in diad sequences on ¹³C nuclear magnetic resonance spectra, preferential and suppressive chain scission of HHx*HB and HB*HHx sequences, respectively, were determined. These specific reaction properties were considered to be contributed by higher steric propyl group in HHx unit than methyl group in HB unit, that is, promoting effect due to the concentration of HHx units in amorphous regions and suppressive effect due to steric hindrance and hydrophobicity of propyl group. Further, it was validated by the lowest-unoccupied molecular orbital analysis using a semi-empirical molecular orbital calculation method.

The spatial distribution of bromine-labeled hydrophobic molecules—bromobenzene (BrBz) and 4-bromobenzylalcohol (BrBzOH)—incorporated in polymer micelles of poly(N,N-dimethylaminoethyl methacrylate)-block-poly(methyl methacrylate) (PDMAEMA-b-PMMA) was investigated using anomalous small-angle X-ray scattering (ASAXS) near the Br K-edge. ASAXS analyses revealed that BrBzOH was homogeneously dispersed in the hydrophobic PMMA core of the PDMAEMA-b-PMMA micelle, whereas BrBz was excluded from the vicinity of the core–shell interface of the PMMA core. The results indicate that the spatial distribution of hydrophobic molecules in polymer micelles strongly depend on the polarity of the encapsulated species.

Polymers that contain arylene groups in their main chain are of significant importance because of their applications to semiconducting materials or engineering plastics. Therefore, controlled methods for the synthesis of arylene-containing polymers based on chain-growth polymerization have been intensively developed in polymer chemistry. This review focuses on the advances in chain-growth polymerization accompanied by formation/introduction of arylene groups into polymer main chains.

Multivariate analysis of ¹³C nuclear magnetic resonance (NMR) spectra successfully evaluated chemical composition and degree of branching value of radically prepared branched copolymers without assigning individual signals, although signals became broadened with increase in branching unit.

Triptycene-based porous organic frameworks (POFs) with high BET (Brunauer–Emmett–Teller) surface and tailored micropore environments were prepared through a facile external knitting strategy. The functionalized POFs exhibited very high aliphatic amine vapor uptakes of up to 5 times of their own weight, and more than 30 times selectivity for aliphatic amines over n-hexane, and thus they open up new opportunities for environment-related applications.

Our recent results in the concurrent cationic vinyl-addition and ring-opening copolymerization of vinyl ethers (VEs) and oxiranes are summarized with particular emphasis on the strategies required to generate crossover reactions between different types of monomers. Most importantly, carbocation generation via the ring-opening reaction of the oxonium ion is indispensable for the crossover reaction from oxirane to VE. This article also summarizes concurrent cationic vinyl-addition, ring-opening and carbonyl-addition terpolymerization, the copolymerization using an alkoxyoxirane through the alkoxy group transfer mechanism and the long-lived species-mediated polymerization using cyclic formals.

Model calculation results for the coefficient of performance c (solid) of a gel actuator driven by the shrinking transition and the increment of the transition temperature (ΔT/T₀) (broken) of the gel plotted against applied force. The shape of these curves depends on the ratio α/β (see text), but the real gels seem to hold α/β >1. In this figure α=3 and β=2 are used for calculation. A reduced form is employed for these variables.

Glycopolymers bearing oligosaccharides with narrow polydispersity indexes (<1.4) were synthesized using a ‘post- click’ chemistry method. A polymer backbone was synthesized by reversible addition-fragmentation chain transfer polymerization with acrylamide derivatives. Maltose, lactose, 3′-sialyllactose and 6′-sialyllactose were added to the polymer backbone and corresponding glycopolymers were obtained. The interactions between the glycopolymers and lectins were evaluated by a quartz crystal microbalance measurement. The interactions between the glycopolymers and influenza viruses were evaluated by hemagglutination inhibition assay.

Magnetic-field-induced alignment of low-molecular-weight syndiotactic polystyrene (sPS) has achieved. Isothermal crystallization from the melting state containing local ordered domains under the 2 or 10 T of the magnetic-field-induced alignment of sPS crystals. The crystalized sPS samples formed the β phase, and the b-axis was aligned parallel to the magnetic field. Low molecular weight of sPS and high magnetic field were effective for high alignment degree. A stepwise crystallization attained higher alignment of sPS compared with an isothermal crystallization.

Interface manipulation to pursue unusual nanostructures was performed using a strategically designed triblock terpolymer with a short middle segment, poly(styrene-b-methyl methacrylate-b-2,2,2-trifluoroethyl methacrylate). A short middle segment of poly(methyl methacrylate) (PMMA) that does not form any distinct domains was found to play an important role in manipulating the interface between the polystyrene (PS) and poly(2,2,2-trifluoroethyl methacrylate) (PTFEMA) domains and forming unconventional partially continuous oblate cylinders with an oblique lattice, as confirmed by small angle X-ray scattering (SAXS) and dual-axis transmission electron microtomography (TEMT).

A series of poly(ethylene glycol) methyl ether methacrylate (PEGMA) hydrogels have been prepared. The smaller the monomer molecular weight, the higher the crosslinking degree, the lower the hydration. Protein adsorption and bacteria/blood cell attachment tests unveil that PEGMA₅₀₀ hydrogel presents a suitable structure to minimize biofouling. A higher molecular weight of monomers is associated to a higher hydrophilicity, but excess of free water facilitates foulant diffusion. Low molecular weight of monomer does not permit to achieve hydration level good enough to form a protective layer against fouling.