Volume 56 Issue 3, March 2024

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 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.

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.

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.

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.

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.

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).

The aggregation states from the interface to the bulk of the adhesive/adherend is a key to unraveling adhesion at the molecular level. We applied X-ray absorption spectroscopy (XAS) in combination with an Ar gas cluster ion beam (Ar GCIB) to poly(methyl methacrylate) (PMMA) films adsorbed onto a SiO_x/Si(111) surface. GCIB-XAS analysis revealed that the orientation of the C=O group in the side chain of PMMA differs between the region from the SiO_x interface to a distance on the order of 1 nanometer and the bulk PMMA region.