Original Article

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.

Acrylate polymerizations catalyzed by Lewis pairs (LP) composed of B(C₆F₅)₃ and various Lewis bases were investigated using two procedures based on different monomer/catalyst addition sequences. When Lewis bases were added to B(C₆F₅)₃-activated n-butyl acrylate (nBA) (procedure 1), the polymerization proceeded quantitatively using all Lewis bases. In contrast, the type of Lewis base significantly affected the polymerization results when nBA was added to interacting LPs (procedure 2). ¹⁹F nuclear magnetic resonance analysis of the LPs indicated that weakly interacting LPs efficiently initiated the polymerizations in procedure 2.

The depolymerization of super engineering plastics such as polysulfone (PSU) smoothly proceeded in the presence of methanol mediated by sodium hydroxide in 1,3-dimethyl-2-imidazolidinone (DMI) at 80 °C to form bis(4-methoxyphenyl)sulfone and 4,4’-(propane-2,2-diyl)diphenol (bisphenol A) in high yields. These products were readily isolated by simple filtration. The DMI solvent effectively promoted depolymerization and allowed insoluble resins such as polyetheretherketone (PEEK) to undergo the reaction. This method was applicable to other alcohols, such as ethanol and isopropyl alcohol.

The hydrogenolysis of PEG-modified soluble lignin was investigated with series of transition metal complexes to afford alkyl guaiacols. Although the introduced PEG moiety was also susceptible against the hydrogenolysis, in situ modification in PEG solvent was found effective for maintaining the lignin soluble and improved degradation efficiency.

A buffer solution of dual stimuli-responsive polymer with photodimerizable groups and temperature-responsive moieties undergoes a phase transition from a sol state to a gel state by exposure to ultraviolet light. The resulting gels changed the physical (elastic modulus) and chemical (hydrophilicity) properties by varying UV exposure time and temperature, respectively. Cell adhesion, spreading, and proliferation were strongly influenced by the physical and chemical properties of the polymer gels, which were regulated by varying UV exposure time and temperature.

We added lithium (trifluoromethane sulfonyl) imide (LiTFSI) salt into an immiscible poly(methyl methacrylate) (PMMA)/ethylene-vinyl alcohol copolymer (EVOH) to improve the transparency and tensile properties. The addition of LiTFSI reduced the refractive index of EVOH, which matched the refractive index of PMMA, resulting in high transparency. In addition, LiTFSI interrupted the intra- and intermolecular hydrogen bonds between the OH groups in EVOH, resulting in decreased crystallinity. Consequently, the amorphous and flexible EVOH domains in the PMMA matrix changed the tensile properties from brittle to ductile by suppressing the stress concentration.

The tensile strength of short carbon fiber (SCF)-reinforced plastics (SCFRPs) prepared by injection molding with various functionalized polypropylenes (PPs) using different types and contents of functional groups and crystallinity, depended on interfacial adhesion. Functionalized PP with more functional groups added to the side chains (PP-g- MA1) exhibited higher interfacial adhesion near the SCFRP surface where the SCF filaments and PP chains were highly oriented in parallel than that with fewer functional groups (PP-t-MA).

Although a fundamental problem, the effect of node functionality on network fracture has yet to be clarified. This study performed phantom chain simulations for networks made from star polymer mixtures with different functionalities. The results reveal that the fracture characteristics lie on the master curves if they are plotted as functions of the cycle rank of the network, irrespective of the mixing ratio and the conversion rate.

Electrically conductive porous materials consisting of cellulose nanofiber (CNF) and graphene were prepared with postreduction processes. Porous CNF/graphene oxide (GO) composites were used as precursors and the reduction of the GO under dry conditions was carried out. Both thermal and chemical reduction processes successfully proceeded to obtain the porous CNF/reduced GO (rGO) composites, in which the conductive path was effectively fabricated owing to the good dispersibility of GO sheets. As a result, the porous CNF/rGO exhibited high electrical conductivity of up to 1.39 × 10^–3 S/m.

The characteristic ratios C_∞ of syndiotactic, isotactic, and atactic hydrogenated ring-opened poly(norbornene)s, H-poly(NB)s, were determined in 1,2,4-trichlorobenzene at 140 °C with molecular dynamics simulations and size exclusion chromatography with a multiangle light-scattering online detector (SEC-MALS). The C_∞ results were 11, 14 and 12 for syndiotactic, isotactic and atactic H-poly(NB), respectively, all of which were consistent with the rotational isomeric state model, and definitely larger than those for polyethylene and polypropylenes. The stiffness of the H-poly(NB) chains was induced by the cyclopentane ring in the chains.

To examine the behavior of degradation by a conjugate substitution reaction in aqueous media, the degradation of a poly(conjugated ester), prepared from 1,4-butylene bis[α-(bromomethyl)acrylate] and fluorescein, with aqueous solution of various nucleophiles was investigated using UV‒vis spectrometry and size-exclusion chromatography. At the earliest stage of the degradation, the affinity between the nucleophile and the polymer affected the reaction rate, leading to faster degradation for relatively hydrophobic amines. On the other hand, hydrophilic nucleophiles that produce water-soluble degradation products promoted complete chain scission.