Research articles

Postpolymerization modifications of poly(2-methoxyethoxycarbonylmethylene) and poly(2-phenoxyethoxycarbonylmethylene) with mixtures of Me₃SiCl and LDA efficiently transformed the alkoxycarbonylmethylene repeating units to ketene silyl acetals to yield a product with up to 93 mol% composition of the latter unit. TBAF-mediated benzylation of the highly silylated polymer with benzyl bromide yielded a polymer containing side chain O (major)- and main chain C (minor)-benzylated units along with the unreacted ketene silyl acetal unit.

This study reports a method that significantly improved the stretchability and damping properties of hydrogels. The innovation is the replacement of traditional short-chain crosslinkers, such as N,N-methylenebis(acrylamide) (MBA), with long-chain crosslinkers. As a result, the molecular chains of the network could slide when stretched, which greatly increased the mechanical elongation and enabled damping by the hydrogel (up to 85%). The maximum elongation reached 21800%, with a toughness of 11.32 MJ m⁻³. This study provides a new approach for the development of highly stretchable and damping hydrogels.

Structural changes induced by thermal denaturation and renaturation of a double-helical polysaccharide xanthan in acidic and basic solutions were investigated mainly by light scattering measurements and circular dichroism spectroscopy. In acidic solution, the renatured components were almost the same as those in native components, while small amounts of aggregates and a hairpin structure were produced via denaturation and renaturation processes. In basic solution, the double helices were dissociated upon heating into the single coils, and high molar mass sample produced a hairpin structure after subsequent renaturation.

The modification of cellulose nanocrystal film using alkyl silane and silane containing tertiary amino groups was performed in a suspension state. Control of the surface structure and functionalization by silane compounds was conducted in the two-stage process. Wettability change property of the silylation-modified CNC triggered by CO₂ was demonstrated.

We examined the adsorption behavior of poly(tert-butyl methacrylate) (PtBMA) and poly(ethyl methacrylate) (PEMA), on a silica surface. Time-evolution of the degree of adsorption γ(t) was evaluated with chip nanocalorimetry. γ(t) revealed a two-step profile for both polymers. At the second stage of adsorption, the slope of γ(t) vs. log t increased as adsorption proceeded; this trend has not been reported for other polymers so far. In addition, atomic force microscopy images of the adsorbed layers revealed corresponding evolutions of the morphologies.

The study on the improvement of the crystallinity of cellulose II by post-treatment with dilute NaOH solution showed that the crystallinity was significantly improved by post-treatment with multiple cycles. The NaOH in an aqueous NaOH solution penetrated only inaccessible surface regions, and cellulose rearrangement occurred only in these regions during post-treatment, improving crystal size. In the second and subsequent posttreatment cycles, cellulose rearrangement occurred only at the inaccessible surfaces expanded during the previous post-treatment cycle, crystallization progressed toward amorphous regions away from the initial crystalline regions.

The fluorophore-modified glucan, TPE-6BG3 adopts an extended, random-coiled form in DMSO, which does not fluoresce. The morphology of the TPE-6BG3 chemosensor changes drastically to a dynamic globule in aqueous media. The dynamic, “induced-fit” globule selectively and sensitively recognizes the medicinally-useful tetrasaccharide, acarbose via glucan-saccharide coaggregation.

Free-standing films of trifluoropropyl-substituted open-cage silsesquioxane-pendant polysiloxane by optimizing sol-gel reaction condition of tris(dimethoxysilyl-ethyl-dimethylsiloxy)-heptatrifluoropropyl-substituted open-cage silsesquioxane. Elastic modulus and the decomposition temperature for 5% weight loss under N₂ of the product by polycondensation at 180 °C were significantly higher than that by polycondensation at 50 °C. Significant changes in the UV-vis spectra of the resulting transparent films were hardly observed even after 13 days of UV irradiation.

Photooxidation and fragmentation behaviors of itPP were studied. Photooxidation likely occurred in the amorphous regions of itPP due to the higher oxygen diffusion. Surface deterioration was observed on the UV-exposed itPP films. Pressed films exhibited much denser cracks compared to uniaxially oriented itPP films. Notably, cracks in the uniaxially oriented itPP films were formed along the direction of orientation and decreased with increasing draw ratio. The crystalline structure and oriented molecular chains notably inhibited the photooxidative degradation and fragmentation of the itPP films.

Steam decomposition of poly(lactic acid) (PLA) and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH) enhanced the recovery of chemical feedstock compared with simple pyrolysis. Steam enhanced the hydrolysis of PLA and resulted in the formation of short-chain compounds with hydroxyl end groups, and subsequent pyrolysis of them improved lactide recovery. Monomer production from PHBH was also enhanced by simultaneous hydrolysis and pyrolysis under steam decomposition.

We developed a novel method for synthesizing degradable polymers based on 1,5-shift radical isomerization polymerizations of vinyl ethers with transferable atoms or groups and in-between acid-cleavable ether linkages in the side chains. In particular, vinyl ethers with side chains composed of thiocyano and p-methoxybenzyl ether groups underwent radical isomerization polymerizations via 1,5-shifts, in which a vinyl ether radical abstracted the cyano group intramolecularly to generate a thiyl radical and result in a polymer with a p-methoxybenzyl ether linkage in the main chain.

We report the syntheses of novel marine biodegradable poly(ethylene succinate) (PES)- and poly(butylene succinate) (PBS)-based copolymers containing different dicarboxylic acid (DCA) units with various carbon numbers and different feed ratios. Specifically, the copolymers with longer-chain DCA units, even at low contents, exhibited marine biodegradability. The thermomechanical properties also varied with the DCA contents. These results indicated that the thermomechanical properties and the marine biodegradability of the PES- and PBS-based copolymers were regulated by controlling their structures and DCA contents.

Hydrogels have attracted considerable attention in the biomedical applications because of their high functionalities, biocompatibility and biodegradability. This study on the novel hyaluronic acid (HA) nanogel-based hydrogel comprising HA modified with cholesterol derivatives and maleimide crosslinking groups. Depending on the degree of cholesterol derivative substitution, the properties such as water uptake, gelation behavior and protein encapsulation was investigated. The results suggested that the hydrogels enhanced peptide and protein trapping abilities have potential as a new hyaluronan hydrogel for biomedical applications.

Overview of the reusable dismantlable adhesion interface system. Heating induces a cleavage reaction of the anthracene photodimer in the molecular layer at the adhesion interface, and the anthracene monomer remains on the substrate surface of the peeled specimen. Photoirradiation to the cleaved molecular layer induces the photodimerization of anthracenes, and the materials exhibit strong adhesion at the adhesion interface.

Fabrication of LCD cell without alignment layer on substrates was achieved via simply adding the chiral polymer nanoparticles into CLC mixtures. The fabricated chiral nanoparticle (CNP) doped CLC cell shows a high contrast 97.4% and a fast response time 7.6 ms.

Aliphatic polycarbonates with ether side groups linked by amide bonds exhibit high hydrolyzability and antiplatelet properties due to enhanced hydration resulting from strong interactions with amide and ether side groups.

To functionalize a poly(isosorbide carbonate) (PIC)-based polymer and evaluate its recyclability, several types of diol comonomers were copolymerized with isosorbide. The thermal and mechanical properties and decomposition behavior of the PIC copolymers were investigated. The thermal stability of PIC was retained, and its glass transition temperature was systematically controlled by copolymerization. The decomposition of the PIC copolymers upon treatment with aqueous ammonia yielded monomers and urea, and the decomposition rate was governed by the structure of the comonomer.

Oligoisoprene macromonomer, which bears a terminal vinyl group and cis-1,4 regularity, was prepared by the metathesis degradation of high-molecular-weight polyisoprene with ethylene in a high selectivity and yield. The ethenolysis is also applicable for the degradation of natural rubber-derived polyisoprene, although the catalytic activity decreased. The prepared oligoisoprene macromonomer was successfully copolymerized with ethylene similarly with 1-hexadecene using a phenoxyimine-ligated titanium catalyst. The oligoisoprene-grafted polyethylene showed a typical stress‒strain curve, of which the tensile modulus and yielding stress are comparable to those of linear low-density polyethylene.

As porous polymer materials with continuous epoxy skeletons and pores, epoxy monoliths exhibit unique mechanical properties and fracture behavior different from the bulk thermoset of epoxy resins. In this article, we describe the thermal properties, pore structures, and mechanical properties of epoxy resins with tensile and compressive deformation of the monoliths. In addition, a change in the inner porous structure after large deformation was nondestructively observed by X-ray CT imaging.

Amine-cured epoxy resins bearing ester moieties were synthesized, and their properties, hydrolytic degradation behavior, and biomineralization were investigated. Neopentyl glycol diglycidate (NPG) was used as the epoxide and was cured with diethylenetriamine and isophoronediamine at different ratios. The T_gs and degradability were controlled using the composition of amines. To demonstrate their potential application as degradable materials for bone and dental repair, composites containing hydroxyapatite were prepared by curing NPG and the amines in the presence of HA. Bone-like apatite was grown on a composite by immersion in synthetic biofluid.