In this study, we prepared stable and flat surfaces of poly(2-methoxyethyl acrylate) (PMEA) which exhibit excellent bio-inert properties in a thin film state by blending it with poly(methyl methacrylate) (PMMA) and annealing at an appropriate temperature, higher than the glass transition temperature and lower than the phase-separation temperature of the blend. Furthermore, the aggregation state and thermal molecular motion of PMEA at the water interface were examined. After contacting with water, PMEA segregated to the water interface in the blend film. While the local conformation of PMEA at the water interface was insensitive to its molecular weight, the local dynamics became faster with decreasing molecular weight, resulting in a disturbance of the network structure of water molecules at the interface. This leads to the extreme suppression of protein adsorption and platelet adhesion.
The catalyst layers in fuel cells are manufactured by drying slurries called catalyst inks. Since cracks which often appear in the catalyst layer affect the performance of fuel cell, it is important to control the formation of the cracks in the manufacturing processes. Understanding the formation mechanisms of cracks helps to control the crack formation. However, the mechanisms are not sufficiently clarified because catalyst inks are complex slurries. In this paper, we investigated the density structures during the drying processes of catalyst layers in a fuel cell by radiography observations using synchrotron X-rays at the SPring-8 BL33XU beam line in order to clarify the crack formations. The results reveal that the cracks are generated at lower density areas than the surroundings as well as at clumps in the drying film. We conclude that controlling both the density distribution during the drying process and the clumps in the catalyst ink is effective for controlling the size and concentration of the cracks.
Here, we investigated the thermal oxidation process of a phenolic antioxidant in polyethylene (PE) by using FT-IR imaging. The peaks of the phenolic group of the antioxidant change by being oxidized with a higher sensitivity than the carbonyl group peak in the FT-IR spectra. Thus it became possible to visualize the oxidation process of PE in more detail. Samples of PE containing a phenolic antioxidant were being kept in air at 60°C for up to 11300 hours, and the following results were obtained. (i) The antioxidant inside PE was not oxidized. (ii) The antioxidant diffused from the inside of PE to the surface, where it was oxidized. (iii) The oxidation started at the surface of PE and the speed of oxidation inside PE was very high because of the low concentration of the antioxidant.
Living cationic cyclopolymerization of 1,2-bis(2-vinyloxyethoxy)-3,5-di-tert-butylbenzene (1) was investigated with the CH3CH(OiBu)OCOCH3/Et1.5AlCl1.5/CH3COOEt initiating system in toluene at 0°C. All the reactions proceeded quantitatively to give gel-free polymers, soluble in organic solvents. The number-average molecular weight (Mn) of the polymers increased in direct proportion to monomer conversion and further increased on addition of a fresh monomer feed to the almost completely polymerized reaction mixture, indicating that living cyclopolymerization of 1 occurred. The content of unreacted vinyl groups in the produced soluble polymers was less than ~2 mol%, and therefore, the degree of cyclization of the polymers was determined to be over ~98%. Preparation of high-molecular-weight cyclopoly(1) was achieved by sequential monomer addition to the living polymerization system and polymer linking reaction of living cyclopoly(1) leading to star-shaped polymers. Glass transition temperature (Tg) of linear cyclopoly(1) (Mn = 18,500) was 134°C and Tg of star-shaped cyclopoly(1) (Mn = 95,900) was 132°C, and thermal decomposition temperatures (Tds) of these cyclopoly(1) were over 350°C, indicating their high thermal stability.
In order to realize drug delivery systems, deeper understanding of the relationship between the position of colloidal particles, flowing in a microchannel, and particle characteristics, such as size and softness, is crucial. However, the influence of the softness of the particles on the flowing position (or segregation) in colloidal mixtures containing polymeric microspheres is still not clear. In this study, we investigated the particle position of binary mixtures in microchannels, observed by an optical microscope equipped with a high-speed camera, and clarified the effect of microgel softness on the segregation. These findings help designing carrier microspheres, for some applications, including drug delivery systems and as artificial blood cells.
In this work, we investigated the direct halogenation of growing species in living anionic polymerization of hydrocarbon monomers for subsequent mechanistic transformation and post-polymerization reactions. The direct halogenation of propagating living anionic species of isoprene (Ip) was examined with CCl4 in THF/methylcyclohexane at −78°C to form a carbon-halogen terminal. The mechanistic transformation from living anionic into radical polymerization was then investigated using the anionically-prepared poly(Ip) (PIp) bearing a chloride terminal as the macroinitiator for the living radical polymerization with the RuCp*Cl(PPh3)/Et3N initiating system in toluene at 80°C, which resulted in the formation of block copolymers of PIp with various radically-polymerized segments. Furthermore, the terminal halogen of the anionically-prepared PIp was also converted into an azide group by SN2 reaction, which could be employed for the click reaction with alkyne-terminated poly(ethylene oxide) by a Cu catalyst to form an amphiphilic block copolymer.
Particle double-network (P-DN) gels are one of the high-strength gels and synthesized by photopolymerization. In this study, a gamma irradiation test was implemented for P-DN gels and the improvement of the radiation tolerance was discussed. Compression tests and water content measurement were carried out for irradiated P-DN gels by 0.1 MGy of cumulated dose. As a result, the compression stress of irradiated P-DN gels decreased to 1/6 in comparison with unirradiated P-DN gels. The water content also decreased with increasing gamma ray dose. It is supposed that new cross-links were generated by radicals, generated by the irradiation. Additionally, compression tests were performed for irradiated P-DN gels, which a radical scavenger added. We confirmed that the decrease of the compression stress was suppressed. Therefore, the radiation tolerance of P-DN gels improved by adding the radical scavenger in the gels.
In this study, aligned-type piezoelectric rubbers with a thickness of 5 mm in which piezoelectric particles were aligned in the direction parallel to the thickness by an electric field were fabricated in order to decrease the spring constant. Numerical simulations of ferroelectric particle alignment by an electric field were also carried out. Our method in which moldings were inverted before applying an electric field led to longer particle alignments for piezoelectric rubbers with 10–20 Vol% of particles, which led to an enhancement of their piezoelectric property. The method was modified to control particle position before applying an electric field and the piezoelectric property of piezoelectric rubber with 30 Vol% of particles was enhanced. Furthermore, the particle alignment was affected by particle position before applying an electric field in numerical simulation. Spring constants of thicker piezoelectric rubbers were compared to previously prepared thinner ones.
A urethane acrylate derived from castor oil was synthesized using castor oil with 2-acryloyloxyethyl isocyanate and obtained in high yield. Furthermore, the obtained urethane acrylate was subjected to a UV cure reaction with polybutadiene. The UV cured film was characterized by thermal and mechanical measurements. The thermal stability of the obtained film was measured by TGA, and 20% thermal weight loss temperature at 425°C was observed. The glass transition temperature of the product was −60°C as revealed by DMA. The Young’s modulus of the product was 2.00 MPa, taken from the stress-strain curve.
Here, we demonstrate that the direct arylation polycondensation of fluoroarenes with dibromoarenes proceeds efficiently under the conditions that we have previously reported for the synthesis of other polymers. The polycondensation of 18.104.22.168-tetrafluorobenzene, 1,2,3,5-tetrafluorobenzene or 2,2′,3,3′,5,5′,6,6′-octafluorobiphenyl with 5,5′-dibromo-3,3′-dihexyl-2,2′-bitiophene, 3,6-dibromo-N-octylcarbazole or 4,4′-dibromo-N-(2-ethylhexyl)diphenylamine in the presence of palladium acetate (2.5 mol%), di-tert-butylmethylphosphonium tetrafluoroborate (5.0 mol%), acetic acid (2 eq.), and potassium carbonate (6 eq.) in toluene (0.5 mL) at 120°C for 24 h gave the corresponding alternating polymers.