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91.
Toshimitsu Ichimori Shinichi Yamazaki Kunio Kimura 《Journal of polymer science. Part A, Polymer chemistry》2011,49(21):4613-4617
The influence of shear flow, especially the timing for the application of shearing, was examined to enhance the selectivity for the preparation of poly(p‐oxybenzoyl) (Pp‐OB) by using hydrodynamically induced phase separation during polymerization of 4‐(4‐acetoxybenzoyloxy)benzoic acid (p‐ABAD) and m‐acetoxybenzoic acid (m‐ABA). The polymers containing few m‐oxybenzoyl (m‐OB) moieties were obtained as precipitates even at high content of m‐OB moiety in feed (χf) under shear flow. The content of m‐OB moiety in the precipitates (χp) prepared under shearing throughout the polymerization at the shear rate (γ) of 489 s?1 was 6.3 mol % even at χf of 60 mol %. Especially, the Pp‐OB was obtained as the precipitates at χf of less than 50 mol %. The timing of the application of the shearing influenced the selectivity significantly, and the shearing just after the precipitation of the oligomers started was quite efficient to enhance the selectivity more. The χp of the precipitates prepared with shearing at γ of 489 s?1 just after the precipitation was only 3.9 mol % even at χf of 60 mol %. The shear flow reduced the difference in the reactivity between p‐ABAD and m‐ABA, resulting in the decrease in the selectivity with regard to the formation of p‐oxybenzoyl homo‐oligomer. However, the shear flow enhanced the difference in the miscibility between homo‐oligomers and co‐oligomers. This change in the miscibility by shear flow brought about the more rapid precipitation of homo‐oligomers, leading to the enhancement of the selectivity. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011 相似文献
92.
Masahiro Kihara Shin‐Ichiro Kohama Shota Umezono Kanji Wakabayashi Shinichi Yamazaki Kunio Kimura 《Journal of polymer science. Part A, Polymer chemistry》2011,49(5):1088-1096
Poly(p‐oxybenzoyl) (POB) crystals were prepared by reaction‐induced crystallization during direct polymerization of p‐hydroxybenzoic acid in the presence of boronic anhydrides. Polymerizations were carried out at 300 °C in dibenzyltoluene at a concentration of 1% with three kinds of anhydrides of boronic acid such as 3,4,5‐trifluorophenylboronic acid (TFB), 4‐methoxyphenylboronic acid (MPB) and 4‐biphenylboronic acid (BPB). The POB crystals were formed as precipitates in the solution and the morphology was considerably influenced by both the structure of the boronic anhydride and its concentration (cB). Needle‐like crystals were firmed in the presence of TFB anhydride (TFBA) at cBs of 5 and 10 mol % by the spiral growth of lamellae. Spherical aggregates of slab‐like crystals were formed at cBs from 50 to 100 mol %. The polymerization with MPB anhydride and BPB anhydride (BPBA) also yielded the needle‐like crystals at cBs of 50 and 5 mol %, respectively. The polymerization with TFBA at lower cB was favorable to prepare the needle‐like crystal. Molecular weight was also influenced by the structure of the boronic anhydride and cB. Mn increased generally with cB and BPBA gave the highest Mn of 14.7 × 103 at cB of 100 mol %. The loose packing of the molecules in the crystal caused by the bulkiness of the end‐groups made the polymerization in the crystals more efficiently. Morphology and molecular weight of the POB crystals could be controlled by the chemical structure and the content of boronic anhydride. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011. 相似文献
93.
94.
Toshinobu Kanai Hiroki Ishibashi. Yoshikazu Hayashi Kunio Oka Takaaki Dohmaru Tatsuo Ogawa Shoji Furukawa Robert West 《Journal of Polymer Science.Polymer Physics》2001,39(11):1085-1092
The thermochromic behavior of poly(di‐n‐octylsilane) {[Si(C8H17)2]n; PDOS} was studied by ultraviolet (UV) absorption, differential scanning calorimetry, and X‐ray diffraction measurements. The structure of PDOS in the low‐temperature phase strongly depended on not only the temperature but also the rate of cooling, that is, the thermal history. Temperature‐dependent UV absorption spectra were highly dependent on thermal hysteresis. Cooled rapidly (10 K/min), PDOS showed two absorption peaks at 3.32 and 3.51 eV in low‐temperature‐ordered phases, whereas a single absorption peak at 3.32 eV became predominant with slow cooling (0.3 K/min). The appearance of the two peaks at low temperatures suggested that a mixture of different conformations was introduced by rapid cooling. A fiber diffraction pattern measured at 240 K after rapid cooling also showed evidence of the existence of novel conformation. A temperature‐dependent powder X‐ray diffraction pattern changed significantly between 270 and 280 K. Rapid cooling reduced the intensity of the X‐ray diffraction peak in this temperature region. This intensity change was explained by the conformational mixture in the polymer. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 1085–1092, 2001 相似文献
95.
A 5-amino-8-hydroxyquinoline (AHQ)-modified gold nanoparticle (GNP) layer was fabricated on an inner wall of a silica capillary column by alternatively passing a citrate-stabilized GNP solution and an AHQ solution in a repeating fashion. The observations by a field emission scanning electron microscope showed that the thickness of the resulting GNP layer was about 0.15 microm. This column was then used as an open tubular solid-phase extraction column for cadmium, followed by electrothermal atomic absorption spectrometric determination. The detection limit of 0.009 ng ml(-1) was obtained. 相似文献
96.
In the article, we study the structure of Galois coverings of self-injective artin algebras with infinite cyclic Galois groups. In particular, we characterize all basic, connected, self-injective artin algebras having Galois coverings by the repetitive algebras of basic connected artin algebras and with the Galois groups generated by positive automorphisms of the repetitive algebras. 相似文献
97.
D. Watanabe H. Ohoyama M. Takahashi T. Kasai 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,38(1):29-34
The total attenuation cross-section of Rg (3P2) (Rg = Ar, Kr) by
the collision with CF3Br is measured as a function of the magnetic sub
level MJ of Rg (3P2) and the collision energy. For Ar
(3P2), the attenuation process indicates a MJ dependence, in
particular, the cross-section of the MJ = 0 state is lower compared
with that for other states. On the other hand, Kr (3P2) shows no
MJ dependent attenuation. 相似文献
98.
Ken Naitoh Yasuo Takagi Kunio Kuwahara Egon Krause Katsuya Ishii 《Fluid Dynamics Research》1990,6(5-6):277-294
The transition to turbulent flow in the compression stage of a reciprocating engine is studied by obtaining the finite-difference numerical solutions to the governing Navier-Stokes equations without using explicit turbulence models. A computational method is developed under the assumption that the flow is in a low-subsonic regime with strong compression. The numerical method is a simple extension of the well known MAC method. Computations were performed for three different chamber geometries at the engine speed of 1400 rpm. The results of the computations clearly demonstrate the transient process in which large tumbling vortices break down into smaller ones near the end of the compression process. The transition process is also caught experimentally by using Mach-Zehnder interferometry. 相似文献
99.
100.
Werner Paschinger Kunio Yubuta Yuta Saiga Toshiro Takabatake Gerald Giester Peter Rogl 《ChemInform》2016,47(29):no-no
Single crystals of Ce3Pt4Sn6 (I) and Ce1‐xPt6Al13+2x (x = 0.207, (II)) are isolated by mechanical fragmentation of specimens grown from self‐fluxes (Sn or Al, resp.) by slow cooling from the melt. 相似文献