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111.
Self-assembled structures in solvent-cast films of binary mixtures of poly(styrene-block-isoprene) (SI) and homo-polystyrenes (HS) were studied as a function of rs, the ratio of molecular weights of HS and polystyrene block (PS) in SI and of wHS, the weight fraction of HS. For rS<1 (a criterion for “wet brush”), HS tends to be solubilized into the microdomain of PS and to swell the PS chains, causing a change in microdomain morphology with long-range order. Spherical microdomains composed of polyisoprene block (PI) dispersed randomly in the matrix of HS and PS (“spherical micelles”) are formed at the limit of high wHS (wHS→1). For rS≳1 (a criterion for “dry brush”), HS tends either to be segregated from SI, forming a macrophase-separated morphology (at rS>>1), or to be solubilized into the PS microdomains without swelling PS or without a significant change of a degree of swelling with wHS, if any, (at rS≌1). In the latter case, HS does not significantly affect the lamellar domains of PI for the particular SI studied here, which by itself gives alternating lamellar microdomains of PS and PI, but increases the mean distance between them. AS wHS→1, the long-range spatial order of the PI lamellae is lost, while keeping their thicknesses constant and uniform, resulting in morphologies of lamellar, cylindrical, and spherical vesicles. The vesicular morphology was analyzed by small-angle X-ray scattering and transmission electron microscopy. At rS>>1 (still in the criterion of dry brush), SI and HS undergo macrophase separation, forming SI domains composed of alternating lamellae in the matrix of HS. 相似文献
112.
Dr. Tsuyoshi Murata Kenta Yoshida Dr. Shuichi Suzuki Dr. Akira Ueda Dr. Shinsuke Nishida Dr. Junya Kawai Dr. Kozo Fukui Prof. Dr. Kazunobu Sato Prof. Dr. Takeji Takui Prof. Dr. Kazuhiro Nakasuji Prof. Dr. Yasushi Morita 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(52):e202201426
A novel neutral diradical of π-extended phenalenyl derivative having three oxo-groups, tri-tert-butyl-1,4,7-trioxophenalenyl, and two types of the corresponding σ-dimers were investigated. Quantum chemical calculations showed that the neutral diradical is in triplet ground state having doubly degenerate singly occupied molecular orbitals. The neutral diradical undergoes a σ-dimerization, generating two types of σ-dimers immediately after the preparation. One of the σ-dimers, which was selectively generated in the crystalline state, was a close-shell dimer linked through double-σ-bonds on the phenalenyl skeleton with a long C−C bond length of 1.66 Å. The other σ-dimer, which existed only in the solution state, was a peroxy-linked open-shell dimer in which one σ-bond was formed between two oxygen atoms. Furthermore, the temperature-dependent 1H NMR and ESR spectra revealed that these σ-dimers are in equilibrium in the solution state by the reversible σ-bond formation/cleavage via the neutral diradical as a key intermediate. 相似文献
113.
Indra Saptiama Dr. Yusuf Valentino Kaneti Prof. Brian Yuliarto Dr. Hiroaki Kumada Dr. Kunihiko Tsuchiya Dr. Yoshitaka Fujita Dr. Victor Malgras Dr. Nobuyoshi Fukumitsu Prof. Takeji Sakae Dr. Kentaro Hatano Prof. Katsuhiko Ariga Prof. Yoshiyuki Sugahara Prof. Yusuke Yamauchi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(18):4843-4855
The effective utilization of various biomolecules for creating a series of mesoporous boehmite (γ-AlOOH) and gamma-alumina (γ-Al2O3) nanosheets with unique hierarchical multilayered structures is demonstrated. The nature and concentration of the biomolecules strongly influence the degree of the crystallinity, the morphology, and the textural properties of the resulting γ-AlOOH and γ-Al2O3 nanosheets, allowing for easy tuning. The hierarchical γ-AlOOH and γ-Al2O3 multilayered nanosheets synthesized by using biomolecules exhibit enhanced crystallinity, improved particle separation, and well-defined multilayered structures compared to those obtained without biomolecules. More impressively, these γ-AlOOH and γ-Al2O3 nanosheets possess high surface areas up to 425 and 371 m2 g−1, respectively, due to their mesoporous nature and hierarchical multilayered structure. When employed for molybdenum adsorption toward medical radioisotope production, the hierarchical γ-Al2O3 multilayered nanosheets exhibit Mo adsorption capacities of 33.1–40.8 mg g−1. The Mo adsorption performance of these materials is influenced by the synergistic combination of the crystallinity, the surface area, and the pore volume. It is expected that the proposed biomolecule-assisted strategy may be expanded for the creation of other 3D mesoporous oxides in the future. 相似文献
114.
Dr. Tsuyoshi Murata Dr. Noriaki Asakura Dr. Ryotaro Tsuji Dr. Yuki Kanzaki Prof. Kazunobu Sato Prof. Takeji Takui Prof. Yasushi Morita 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(12):e202104447
A new silyl-substituted trioxotriangulene ( TOT ) neutral radical and corresponding porous organosiloxanes (POSs) were synthesized. The neutral radical exhibited a peculiarly high stability and formed a diamagnetic π-dimer characteristic to TOT neutral radicals stabilized by the strong multiple SOMO-SOMO interaction in both solution and solid states. POSs including TOT units within the organosiloxane-wall were prepared by polycondensation of the silyl groups and formed microporous structures with ∼1 nm-size diameters. Redox ability of TOT units in the POS was demonstrated by the treatment of oxidant/reductant in heterogeneous suspension condition, where the TOT units were reversibly converted between reduced and neutral radical species. Furthermore, the solid-state electrochemical measurements of the POS revealed the reversible multi-stage redox ability of TOT units involving polyanionic species within the organosiloxane-wall. 相似文献
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116.
Hiroki Murase Takuji Kume Takeji Hashimoto Yasuo Ohta Tohru Mizukami 《Macromolecular Symposia》1996,104(1):159-182
The shear-induced concentration fluctuations or phase separation of a semidilute solution comprised of polystyrene (PS) as a solute and dioctylphthalate (DOP) as a solvent (PS/DOP) was investigated by using real-time and in-situ shear-small-angle light scattering and shear-phase-contrast optical microscopy. When a transient shear flow with a fixed shear rate γ greater than a critical value γC was imposed on the solution, a unique anisotropic scattering pattern was observed some time after onset of shear. This pattern was found to be identical to the “butterfly pattern” previously reported for the same solutions under steady shear flow with γC. When the shear flow was ceased before the scattered intensity reached a steady state, the scattered intensity rapidly increased toward a maximum intensity, and then decreased toward the intensity of the quiescent solution with time. From the phase-contrast microscopy, this immediate increment of the scattered intensity after the shear cessation was found to arise from the increment in amplitude of the concentration fluctuations along flow direction. The characteristic length scale of the fluctuations was about 2.5 μm in this experiment, almost independent of the shear rate imposed on the solution. 相似文献
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119.
Yasuo Ohta Hiroki Murase Takeji Hashimoto 《Journal of Polymer Science.Polymer Physics》2005,43(19):2639-2652
We investigated the tensile strength and modulus of ultrahigh‐strength polyethylene (UHSPE) fibers obtained by using the special two‐step‐drawing process of as‐spun fiber (ASFs) which were prepared by the so‐called gel‐spinning method. We have found that the higher the ASF's spinning speed is, the higher the attainable tensile strength σf and modulus E are. For all the fibers drawn from ASFs with various spinning speed except for 120 m/min, we have found a master curve for the inverse of σf which is plotted as a function of T1/4E?1/2, where T is the linear density of the drawn fibers, in consistent with the Griffith theory: a thicker fiber obtained with a lower spinning speed exhibits lower strength, although all the AFSs possess the same value of E. This also suggests that a thicker fiber contains more defects which would lead to the Griffith‐type crack propagation breakage. Moreover, from morphological observation of ASFs under transmission electron microscopy, the ASF obtained at a relatively low spinning speed possesses a heterogeneous cross‐sectional morphology, whereas that obtained at relatively high spinning speed possesses a relatively homogenous morphology. We propose that this morphological evidence may account for the experimental findings of the behavior of the mechanical properties described above. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2639–2652, 2005 相似文献
120.
Endoh MK Takenaka M Inoue T Watanabe H Hashimoto T 《The Journal of chemical physics》2008,128(16):164911
We aimed at elucidating the influence of shear-induced structures (shear-enhanced concentration fluctuations and/or shear-induced phase separation), as observed by rheo-optical methods with small-angle light scattering under shear flow (shear-SALS) and shear-microscopy, on viscoelastic properties in semidilute polystyrene (PS) solutions of 6.0 wt % concentration using dioctyl phthalate (DOP) as a Theta solvent and tricresyl phosphate (TCP) as a good solvent. In order to quantify the effects of the shear-induced structures, we conducted a numerical analysis of rheological properties in a homogeneous solution based on the constitutive equation developed by Kaye-Bernstein, Kearsley, and Zapas (K-BKZ). In the low-to-intermediate shear rate gamma region between tau(w) (-1) and tau(e) (-1), where tau(w) and tau(e) are, respectively, terminal relaxation time and the relaxation time for chain stretching, the steady state rheological properties, such as shear stress sigma and the first normal stress difference N(1), for the PS/DOP and PS/TCP solutions are found to be almost same and also well predicted by the K-BKZ equation, in spite of the fact that there is a significant difference in the shear-induced structures as observed by shear-SALS and shear-microscopy. This implies that the contribution of the concentration fluctuations built up by shear flow to the rheological properties seems very small in this gamma region. On the other hand, once gamma exceeds tau(e) (-1), sigma and N(1) for both PS/DOP and PS/TCP start to deviate from the predicted values. Moreover, when gamma further increases and becomes higher than gamma(a,DOP) (sufficiently higher than tau(e) (-1)), above which rheological and scattering anomalies are observed for PS/DOP, sigma and N(1) for PS/DOP and PS/TCP are significantly larger than those predicted by K-BKZ. Particularly, a steep increase of sigma and N(1) for PS/DOP above gamma(a,DOP) is attributed to an excess free energy stored in the system via the deformation of interface of well-defined domains, which are aligned into the stringlike structure developed parallel to the flow axis, and stretching of the chains connecting the domains in the stringlike structures. Thus, we advocate that the effect of shear-induced structures should be well considered on the behavior of sigma and N(1) at the high gamma region above tau(e) (-1) in semidilute polymer solutions. 相似文献