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31.
Yuto Kurasaki Yasuhito Suzuki Akikazu Matsumoto 《Journal of polymer science. Part A, Polymer chemistry》2020,58(7):923-931
We carried out the thermal curing of the copolymers of N-allylmaleimide (AMI) and 2-ethylhexyl acrylate (2EHA) using 1,3,4,6-tetra(2-mercaproethyl)glycoluril ( G1 ), 1,3,4,6-tetra(3-mercaptopropyl)glycoluril ( G2 ), 1,3,4,6-tetraallylglycoluril ( G3 ), triallylisocyanurate (TAIC), and pentaerythritol tetrakis(3-mercaptobutyrate) (PEMB) as the crosslinkers. Based on the results for the analysis of thiol–ene reactions monitored by IR spectroscopy, it was confirmed that the curing rate significantly depended on the combination of the used crosslinkers. The insoluble fraction after curing was more than 90% for the systems using the glycoluril crosslinkers, while the conversion of the allyl groups was suppressed due to the rigid structure of these crosslinkers. The heat resistance and the mechanical properties of the crosslinked polymers were investigated by thermogravimetric analysis, differential scanning calorimetry, dynamic mechanical analysis, and mechanical tensile tests. For the products cured using the glycoluril crosslinkers, the glass transition temperature (Tg) and the maximum temperature of thermal decomposition (Tmax) were 54–59 °C and 395–409 °C, respectively, being higher than those for the cured product prepared with PEMB and TAIC as the conventional crosslinkers. The elasticity (75–139 MPa), the maximum strength (3.0–4.1 MPa), and the adhesion strength (6.7–10.7 MPa) for the polymers cured with the glycoluril crosslinkers, determined by the mechanical tensile and single lap-shear adhesion tests, were higher than those for cured materials produced with PEMB. Thus, the thermal and mechanical properties of the maleimide copolymers were efficiently enhanced by crosslinking using the rigid glycoluril compounds. © 2020 Wiley Periodicals, Inc. J. Polym. Sci. 2020 , 58, 923–931 相似文献
32.
The vapor growth of GaxAl1?xSb was experimentally studied using a closed tube transport technique. In the closed tube process with iodine as a transport agent, GaxAl1?xSb was successfully grown on (111) oriented GaSb substrates at a relatively low temperature. The composition of the grown layer depended primarily on that of the source, and had only a small graded region (<0.5 μm) between the substrate and the epitaxial layer. The growth rate was almost constant irrespective of the growth time, whenever the other growth parameters were unchanged. 相似文献
33.
[reaction: see text] We have found the first example of high levels of asymmetric induction (97-74% ee) along with high diastereoselectivity (>99:1-64:36) in dipole-HOMO-/dipolarophile-LUMO-controlled asymmetric 1,3-dipolar cycloaddition reactions between fused azomethine imines and 3-acryloyl-2-oxazolidinone using a chiral BINIM-Ni(II) complex as a chiral Lewis acid catalyst. 相似文献
34.
Some bis(indolizin-1-yl) disulfides, readily obtainable from the treatment of 1-(benzoylthio)indolizines with piperidine, were prepared and their conformations were investigated. In comparison with those of 1-(benzoylthio)indolizines, the (1)H-NMR spectra of these disulfides showed considerable high field shifts (delta 0.13-0.82 ppm) on each pyridine ring proton and the UV spectra exhibited significant bathochromic and hyperchromic shifts. These results supported strongly the participation of an intramolecular pi-pi interaction between the two indolizine rings in these molecules and, hence, of a particular gauche (cis) conformation. However, the conformational considerations and molecular calculations (Mopac PM3) for some bis(indolizin-1-yl) disulfides showed the presence of four more stable gauche forms in which two are enantiomeric, resulting in three types of gauche structures. These three types of gauche structures were confirmed by X-ray analyses. 相似文献
35.
Akikazu Matsumoto Ryo Hiuke Toru Doi 《Journal of polymer science. Part A, Polymer chemistry》1997,35(8):1515-1525
The radical copolymerization of N-(2,6-dimethylphenyl)maleimide (DMPhMI) and 2,4,4-trimethylpentene (TP) was investigated in several solvents at 60°C. The copolymerization rate and the molecular weight of the resulting copolymers were dependent on the kind of solvent used. It was also revealed that the monomer reactivity ratios depended on the solvent; r1 = 0.086 and r2 = 0 in chloroform and r1 = 0.25 and r2 = 0 in benzene, where DMPhMI and TP are M1 and M2, respectively. The propagation rate constants were determined for the homopolymerization and copolymerization in chloroform and benzene using electron spin resonance spectroscopy. The homo- and crosspropagation rate constants (k11 and k12, respectively) were revealed to depend on the solvent: k11 is 20 and 37 L/mol·s and k12 is 230 and 150 L/mol·s in chloroform and in benzene, respectively. The interaction between the maleimide moiety and the solvent molecules was discussed based on the acceptivity of the solvents. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 1515–1525, 1997 相似文献
36.
37.
During high-resolution capillary electrophoresis analysis in an electrolyte solution containing a neutral polymer, small oligomers of regularly arranged acidic polysaccharides such as hyaluronic acid and N-acetylneuraminic acid polymers showed reversal of the migration order. This anomalous migration was well correlated with their reported biological activity. In the present study, we analyzed hyaluronidase action on the purified hyaluronic acid oligomers using capillary electrophoresis and found that hydrolytic and transglycosylation actions by hyaluronidase were dependent on the molecular sizes of hyaluronic acid oligomers, and well correlated to their migration profiles. Furthermore, fluorescent polarization technique was employed for understanding the relationship between molecular size of hyaluronic acid oligomers and their electromigrations. 相似文献
38.
Toru Doi Akira Akimoto Akikazu Matsumoto Takayuki Otsu 《Journal of polymer science. Part A, Polymer chemistry》1996,34(3):367-373
Radical copolymerization of N-methylmaleimide (MeMI) as well as other N-alkylmaleimides (RMI) and isobutene (IB) was carried out with 2,2′-azobis(isobutyronitrile) as an initiator at 60°C. The initial rate of the copolymerization (Rp) was dependent on the monomer composition and was maximum at the 40 mol % of MeMI in the feed. A solvent effect on the Rp and the monomer reactivity ratio was observed in this copolymerization system, i.e., copolymerization in chloroform produced a higher Rp and an alternating tendency compared with those in dioxane (rMeMI = 0.14, r1B = 0 in chloroform and rMeMI = 0.47, r1B = 0 in dioxane). The alternating copolymer of RMI and IB shows a high glass transition temperature (Tg) and excellent thermal stability, e.g., the Tg and the thermal decomposition temperature (Td) were 152 and 363°C, respectively, for the alternating copolymer of MeMI and IB. Both the Tg and Td increased as the concentration of the MeMI unit in the copolymers increased. Colorless transparent sheets were obtained from press molding the alternating copolymers. They showed excellent mechanical and optical properties. © 1996 John Wiley & Sons, Inc. 相似文献
39.
Akikazu Matsumoto Yoshinori Sano Masahiro Yoshioka Takayuki Otsu 《Journal of polymer science. Part A, Polymer chemistry》1996,34(2):291-299
The radical polymerization of dialkyl fumarates (DRF) bearing various ester alkyl groups was kinetically studied. The propagation and termination rate constants were determined using electron spin resonance (ESR) spectroscopy. The introduction of the bulky ester alkyl groups such as a tert-butyl group decreased the termination rate constant as expected. However, it has also been revealed that the bulky groups promote propagation despite the steric repulsion. The propagation rate and mechanism are discussed in relation to the propagation manner, i.e., tacticity of the polymer. © 1996 John Wiley & Sons, Inc. 相似文献
40.
The radical polymerization kinetics and mechanism of sterically hindered dialkyl fumarates (DRF) bearing various ester alkyl groups are described comprehensively. The overall polymerization reactivity of DRF, the initiation mechanism and the reactivity of the primary radicals in the polymerizations with azo initiators, the determination of the propagation and termination rate constants by means of electron spin resonance spectroscopy, the propagation mechanism and the microstructure of the polymers, and the chain rigidity of poly(DRF) and bimolecular termination process are discussed. 相似文献