Redox-responsive supramolecular polymeric networks having double-threaded inclusion complexes

Stimuli-responsive hydrogels have attracted attention as soft actuators that act similarly to muscles. In this work, hydrogel actuators controlled by host–guest interactions have been developed. The introduction of a 1:1 inclusion complex into a hydrogel is a popular design for achieving a change in cross-linking density. To realize faster and larger deformation properties, the introduction of a 1:2 inclusion complex is effective because the alteration in cross-linking density in a hydrogel with 1:2 complexes is larger than that in a hydrogel with 1:1 complexes. A redox-responsive hydrogel actuator cross-linked with 1:2 inclusion complexes is designed, where γ-cyclodextrin (γCD) and viologens modified with an alkyl chain derivative (VC11) were employed as the host and guest units, respectively. γCD includes two VC11 molecules in its cavity. The obtained γCD–VC11 hydrogel cross-linked with the 1:2 complex showed faster and larger deformation behaviour than the αCD–VC11 and the βCD–VC11 hydrogels cross-linked with a 1:1 complex. The deformation ratio and response speed of the γCD–VC11 hydrogel, which forms a supramolecular cross-linking structure by stimuli, are 3 and 11 times larger, respectively, than those of our previous hydrogel consisting of a βCD/ferrocene 1:1 inclusion complex.

A hydrogel actuator with a 1:2 host–guest complex controlled by redox stimuli has been developed to realize faster and larger deformation.     

Polymerizability and related problems in the anionic polymerization of lactams

The anionic polymerization of lactams at low temperatures is not governed by thermodynamic equilibrium between the cyclic monomer and the linear polymer. On the basis of our reaction mechanism we propose therefore a new criterion (in contrast to the thermodynamic one) for estimating the chemical polymerizability of lactam: k_endo/k_lactam, where k_lactam is the rate constant of alkaline hydrolysis of the lactam and k_endo that of the endocyclic imide bond in the corresponding N-acyl lactam. The value thus found for α-piperidone and giving the theoretical polymerizability of this lactam accounts, however, only partially for its low polymerizability. Finally, the behavior of α-piperidone derivatives in α-pyrrolidone polymerization, as well as that of α-pyrrolidone and α-piperidone in polymerization in the presence of inorganic salts such as LiCl and LiSCN, shows that the unusually low ability of this lactam to polymerize could be explained in terms of the hydrogen-bond-rich structure of the resulting polymer appearing at a lower stage of conversion than that of other lactams and which might encage the active site situated at the end of the growing chain and thus hinder the access of lactam anion.     

Efficient intramolecular Diels–Alder reactions of ester-tethered 1,7,9-decatrienoates catalyzed by bis-aluminated trifluoromethanesulfonamide

Bis-aluminated trifluoromethanesulfonamide generated in situ by mixing TfNH₂ (1 mol) and methylaluminum reagent (2 mol) is an effective catalyst for the IMDA reaction of ester-tethered 1,7,9-decatrienoates.     

Time-series analysis of sleep-wake stage of rat EEG using time-dependent pattern entropy

We performed electroencephalography (EEG) for six male Wistar rats to clarify temporal behaviors at different levels of consciousness. Levels were identified both by conventional sleep analysis methods and by our novel entropy method. In our method, time-dependent pattern entropy is introduced, by which EEG is reduced to binary symbolic dynamics and the pattern of symbols in a sliding temporal window is considered. A high correlation was obtained between level of consciousness as measured by the conventional method and mean entropy in our entropy method. Mean entropy was maximal while awake (stage W) and decreased as sleep deepened. These results suggest that time-dependent pattern entropy may offer a promising method for future sleep research.     

Chiral Kosterlitz-Thouless transition in the frustrated Heisenberg antiferromagnet on a pyrochlore slab

Ordering of the geometrically frustrated two-dimensional Heisenberg antiferromagnet on a pyrochlore slab is studied by Monte Carlo simulations. In contrast to the kagomé Heisenberg antiferromagnet, the model exhibits locally noncoplanar spin structures at low temperatures, bearing nontrivial chiral degrees of freedom. Under certain conditions, the model exhibits a novel Kosterlitz-Thouless-type transition at a finite temperature associated with these chiral degrees of freedom.     

Development of the 8-aza-3-bromo-7-hydroxycoumarin-4-ylmethyl group as a new entry of photolabile protecting groups

A significant substitution effect of the position of the bromo group on the photosensitivity of the 8-azacoumarin chromophore leads to the development of a highly photosensitive 8-aza-3-bromo-7-hydroxycoumarin-4-ylmethyl (aza-3-Bhc) group that shows excellent photolytic efficiency and hydrophilicity with long-wavelength absorption maxima. The newly identified aza-3-Bhc group can be applied to caged glutamates for ester-type and carbamate-type protections of carboxyl and amino functionalities.     

2-Acyl-tetrahydroisoquinoline-3-carboxylic acids: lead compounds with triple actions, peroxisome proliferator-activated receptor α/γ agonist and protein-tyrosine phosphatase 1B inhibitory activities

2-Acyl-tetrahydroisoquinoline-3-carboxylic acid derivatives were synthesized and biologically evaluated. (S)-2-(2,4-Hexadienoyl)-7-[2-(5-methyl-2-phenyloxazol-4-yl)ethoxy]-1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid (14) showed peroxisome proliferator-activated receptor γ (PPARγ) and PPARα agonist activities and protein-tyrosine phosphatase 1B (PTP-1B) inhibitory activities. PPARγ agonist activity of 14 was comparable to that of rosiglitazone, and PTP-1B inhibitory activity was about 10-fold weaker than that of ertiprotafib, a PTP-1B inhibitor. Compound 14 showed high oral absorption in rats and potent hypoglycemic effects in KK-A(y) mice. In conclusion, 14 would be an excellent lead compound for a new type of anti-diabetic drug with triple actions.     

Proton Conductivities of Graphene Oxide Nanosheets: Single,Multilayer, and Modified Nanosheets

Proton conductivities of layered solid electrolytes can be improved by minimizing strain along the conduction path. It is shown that the conductivities (σ) of multilayer graphene oxide (GO) films (assembled by the drop‐cast method) are larger than those of single‐layer GO (prepared by either the drop‐cast or the Langmuir‐Blodgett (LB) method). At 60 % relative humidity (RH), the σ value increases from 1×10⁻⁶ S cm⁻¹ in single‐layer GO to 1×10⁻⁴ and 4×10⁻⁴ S cm⁻¹ for 60 and 200 nm thick multilayer films, respectively. A sudden decrease in conductivity was observed for with ethylenediamine (EDA) modified GO (enGO), which is due to the blocking of epoxy groups. This experiment confirmed that the epoxide groups are the major contributor to the efficient proton transport. Because of a gradual improvement of the conduction path and an increase in the water content, σ values increase with the thickness of the multilayer films. The reported methods might be applicable to the optimization of the proton conductivity in other layered solid electrolytes.