Note in 2024

The Poisson's ratio (μ) of natural rubber undergoing strain-induced crystallization was studied across a broad stretch range. Below the crystallization onset stretch (\({\lambda }_{{||}}\)* ≈ 4.1), μ remains near 0.5, indicating incompressibility. Beyond \({\lambda }_{{||}}\)*, μ decreases with increasing crystallinity, reaching 0.33 at fracture (\({\lambda }_{{||}}\) ≈ 7.1), as the matrix transforms from amorphous to semicrystalline. The true stress at fracture, accounting for lateral contraction, is approximately 85% of the estimated value assuming μ = 0.5. These insights are vital for modeling the mechanical behavior of strain-crystallizing elastomers.

The glass transition temperature of the dry polymers (T_g,dry) is a useful parameter for predicting that of hydrated polymers (T_g,wet). By combining T_g,dry and chemical structures, simple machine learning models for T_g,wet can be constructed even with a small dataset.

Selective deprotection of tertiary-butyl (tert-Bu) ester in poly(n-butyl methacrylate-b-tert-butyl methacrylate) was studied via heterogeneous acid catalysts and flow reactors. We found that selective deprotection of tert-Bu ester was achieved successfully using an acidic macroreticular polymeric catalyst, Amberlyst 35DRY, packed in a flow reactor. The deprotection process required 15 min of residence time at 180 °C to give an acidic poly(n-butyl methacrylate-b-methacrylic acid) with a small polydispersity index (Ð) value such as 1.28.

Double-stranded polymers have attracted attention due to their elegant structures and potential properties arising from their topology. In this work, we performed cross-linking polymerization of an active ester acrylate monomer within the nanochannels of a metal‒organic framework (MOF). The spatial constraints in the MOF facilitated the formation of a polymer duplex. Subsequently, transformation of the side chains could be achieved without altering the double-stranded topology, providing a variety of functional vinyl polymer duplexes.

Polyamidoamine dendrimers modified with cis-1,2-cyclohexane dicarboxylic acid and phenylalanine, named PAMAM-CHex-Phe, with various numbers of Phe residues were synthesized as dual pH- and temperature-sensitive polymers. PAMAM-CHex-Phe, with fewer than 32 Phe residues, showed lower critical solution temperature (LCST)-type thermosensitivity at pH 5. PAMAM-CHex-Phe40 and PAMAM-CHex-Phe48 exhibited both LCST- and upper critical solution temperature (UCST)-type thermosensitivity at pH values of 5 and 6, respectively. PAMAM-CHex-Phe64 showed UCST-type thermosensitivity. Our results indicate that thermosensitivity can be regulated by changing the number of Phe residues in PAMAM-CHex-Phe and the solution pH.

Heat insulators are key materials for efficient energy use and reduction of CO₂ emissions. Recently, we examined cross-linked polymethylsilsesquioxane (MSQ) for use as the basic structure of heat-resistant insulation materials. In this study, we prepared MSQs with different cross-linking units and examined the effects of their structures on the heat resistance and heat insulation properties. Among those, MSQ linked by diethynylbenzene had sufficiently low thermal diffusivity and moderately high heat resistance.

The dynamic and structural properties of the water molecules in 3-(1-piperazinyl)-1,2-propanediol-containing polyvinyl alcohol membranes were analyzed by molecular dynamics simulations. The resulting curve of the coordination number with diffusivity yielded important insights into the changes in the state of the water molecules with the water content, clarifying a key factor in determining the membrane performance for CO₂ separation.

For the first time, this paper revealed that 2-picoline borane (pic-BH₃) functioned well in the reductive amination of chitosan. Therefore, N-benzyl chitosan with a nearly perfect degree of substitution was successfully obtained, which has rarely been achieved by other synthetic methods. The new method herein has many advantages, including being more facile, more efficient, and less harmful than conventional methods; thus, this method is applicable to other aldehydes or ketones, leading to a wide variety of N-modified chitosan specimens with desirable degrees of substitution in the future.

This study developed a novel method for the control of the cellulose crystal of cellulose I and II. The crystal transition from cellulose I to II was tracked when cellulose I, which is soaked in a low-concentration NaOH aqueous solution, was quenched using liquid nitrogen. The crystal transition progressed from the surface to the center of the sample. This quench treatment has the potential to fabricate new cellulose materials with a cellulose I core and a cellulose II surface.

The Suzuki–Miyaura coupling reaction of BrC₆H₄-SiRR’-C₆H₄Br 1 with phenylboronic acid 3 in the presence of ^tBu₃PPd precatalyst 4 and CsF/18-crown-6 produced a phenyl-disubstituted product, indicating that the Pd catalyst underwent catalyst transfer on the silylene group. The polycondensation of 1 and phenylenediboronic acid 2 yielded cyclic polymers even when excess 1 was used. The obtained cyclic polymers containing the silylene group showed stronger fluorescence in solution than did the methylene counterpart.

The surface properties of the star polymer coating were evaluated with their resistance to protein adsorption and surface zeta (ζ)-potential to clarify the mechanism for inhibition of cell adhesion. The surface of the star polymer coating with a high density of poly(2-hydroxyethyl methacrylate) formed an electrically neutral diffuse brush structure in water and showed high resistance to protein adsorption. Considering the data obtained in the study, the surface ζ-potential and antibiofouling properties were correlated by controlling the molecular architecture of the coating material.

Surface amino groups (SAGs) on nanochitin materials were quantified using three amino-labeling reagents and two cationic dyes. After binding to SAGs, the excess labeling reagents or generated molecules were assessed by spectrophotometry. The dyes were adsorbed onto SAGs, and the excess was similarly quantified. The obtained values were compared with the titration values. Although the values by labeling reagents were underestimated, some of the values were proportional to those by titration. Reliable results were attained using the two labeling reagents with conversion equations or using Acid Orange 7 adsorption.

The morphology and physical properties of polyisoprene ionomers co-neutralized with Na⁺ and Mg²⁺ in different ratios have been studied. The mechanical and self-healing properties of the ionomer were reinforced and disturbed, respectively, at over 25 % of the Mg²⁺ ratio, where linkage via Mg²⁺ in the network is pervasive throughout the material.

We report the humidity-responsive volume changes of a poly(N-isopropylacrylamide) (PNIPAAm) gel and bending deformation of a PNIPAAm and poly(N,N-dimethylacrylamide) (PDMAAm) complex gel.

To develop a novel gel catalyst system for a selective reaction, we prepared a variety of gels with homogeneously dispersed crosslinked domain (CD) structures containing iridium complexes with various crosslinking densities. The designed CD gel catalyst catalyzed the N-alkylation of aniline with benzyl alcohol, and the steric effect of the CD structure allowed the selective formation of the secondary amine product by controlling the access of the substrate to the iridium complex.