Volume 53 Issue 6, June 2021
Enhanced self-humidification and proton conductivity in magnetically aligned NiO-Co3O4/chitosan nanocomposite membranes for high-temperature PEMFCs
Free-standing, tartaric acid cross-linked chitosan thin films doped with magnetically aligned NiO-Co3O4 filler were successfully synthesized using facile solution-casting method under externally applied magnetic field. The aligned membranes displayed higher proton conductivity than Nafion-212 when measured by both two-probe and four-probe techniques in zero humid conditions. The membranes also showed excellent thermal, oxidation, and mechanical stability.
A series of aliphatic polycarbonate-based polyurethanes with different content of cyclic structure was synthesized. There were more hydrogen bonds between soft and hard segments formed as the content of cyclic units increased. The mechanical and thermal properties of the environment-friendly polycarbonate-based polyurethanes can be enhanced and controlled by varying the content of the cycloaliphatic structures. These polyurethanes can be considered as high potential materials that can be used in different applications in the future.
Microdomain structure change and macroscopic mechanical response of styrenic triblock copolymer under cyclic uniaxial and biaxial stretching modes
The mechanical stretching behavior of poly(styrene-b-ethylene-co-butylene-b-styrene) (SEBS) was investigated under three different stretching modes and through in situ SAXS analysis. SEBS exhibited smaller hysteresis during cyclic equi-biaxial stretching than that of uniaxial stretching. SAXS measurement revealed that affine deformation occurred in the smaller stretching ratio (λ) region for both uniaxial and equi-biaxial stretching modes and deviation from affine deformation occurred for uniaxial stretching mode at the larger λ region. This is because entangled loops of poly(ethylene-co-butylene) chains serves as cross-linking points when films are stretched under equi-biaxial stretching mode.
A microstructured film was fabricated using the breath figure method, and a slippery surface was achieved by infusing silicone oil onto the film. Among the obtained samples, oil-supported pincushion films (oPCF) most efficiently prevented water droplets and microorganisms from adhering to the surfaces. In addition, the adhesion of E. coli and B. subtilis to oPCF was reduced to 7.1 and 13% of that pertaining to PTFE, respectively. These results suggest that our efficient antifouling substrate can ensure human health and environmental safety without the use of any toxic compounds.
Development and chemical properties of retinal prostheses using photoelectric dyes coupled to polyethylene films with various anions to achieve high durability
Our retinal prosthesis, referred to as a dye-coupled film, was developed by chemically coupling photoelectric dyes to the surface of a polyethylene film for restoring retinitis pigmentosa. However, the amount of coupled dye decreased during an implantation test in a monkey’s eye. For improving long-term durability, anion exchange from Br− to PF6−, BF4−, and bis(trifluoromethanesulfonyl)imide (TFSI−) was conducted. The long-term durabilities of the dye-coupled film–PF6−, –TFSI−, and –BF4− improved by 637, 215, and 48%, respectively, indicating that the dye-coupled film–PF6− exhibits the best long-term durability.
Thermoresponsive degradable copolymers and hydrogels were synthesized by radical copolymerization of 2-methylene-1,3-dioxepane (MDO) and N,N-dimethylacrylamide (DMAAm). These prepared materials showed thermoresponsive property through the balance of hydrophobic MDO and hydrophilic DMAAm in the polymer chain. Under alkaline conditions (pH 11.3), these materials degraded and turned into water-soluble oligomers. In addition, the hydrogels self-degraded in PBS due to the decreased pH of the inner hydrogel. The prepared thermoresponsive degradable hydrogels are expected as stimuli-responsive drug delivery carriers and cell culture scaffolds.
Construction of a reduction-responsive oligonucleotide via a post-modification approach utilizing 4-nitrophenyl diazomethane
A reduction-responsive oligonucleotide was successfully constructed by post-modification of an oligonucleotide with a diazo compound bearing a 4-nitrobenzyl group as a reduction-responsive cleavable moiety. High-performance liquid chromatography and mass spectrometry were used to reveal the introduction of the 4-nitrobenzyl group to the 5′-phosphate group of the oligonucleotide, and the subsequent reduction-triggered recovery of the original oligonucleotide. The protocol used for the preparation of this reduction-responsive oligonucleotide is simple and it will have various applications in the fields of chemical and synthetic biology.
Sequence modification in copoly(ester-imide)s: a catalytic/supramolecular approach to the evolution and reading of copolymer sequence information
Catalytic ester-interchange reactions allow new sequence information to be written statistically into poly(ester-imide) chains based on NDI (1,4,5,8-naphthalenetetracarboxylic diimide) units. Insertion of the cyclic ester cyclopentadecanolide (“exaltolide”) into an NDI-based homopolymer and quantitative sequence exchange between two different homopoly(ester-imide)s are both catalyzed by di-n-butyl tin(IV) oxide. Emerging sequences from these reactions are identified using pyrene-d10 as a “reader molecule” that binds rapidly and reversibly to the NDI residues, and amplifies the separation of 1H NMR resonances associated with different sequences via cumulative aromatic ring-current shielding.