Copolymerization of 3,3,3-trifluoro-1,2-epoxypropane with N-phenylmaleimide using organozinc initiators

Novel copolymers consisting of 3,3,3-trifluoro-1,2-epoxypropane (TFEP) and N-phenylmaleimide (PMI) units were prepared by the copolymerization of TFEP with PMI initiated with an organozinc compound. Using [Zn(OCH₃)₂ · (C₂H₅ZnOCH₃)₄] as an initiator, the copolymer chains consisted mainly of TFEP-TFEP sequences. The TFEP-PMI sequence content in the copolymer chains was small. On the other hand, using (C₂H₅ZnOCH₃)₄ as an initiator, only low molecular weight copolymers were formed. Those copolymers were suggested to have block structure, poly(TFEP)-block-poly(PMI), by the ¹⁹F NMR analysis. The copolymers showed higher thermostability than poly-(TFEP).     

Mesomorphic Characteristics of Induced Chiral Nematic Phase of [Smectic LCP,PS(4BC/DM)/Nematic LC,E7/Chiral Dopant,CB-15]-Ternary Composite System

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Interaction between charged soft microcapsules and red blood cells: effects of PEGylation of microcapsule membranes upon their surface properties

Four types of hydrophilic gel microcapsules containing water have been prepared by an interfacial polymerization method. Each type of microcapsules has a membrane of different composition. Using three kinds of monomers, N,N-dimethylacrylamide (DMAAm), 4-(aminomethyl)styrene (AmSt), and N,N-dimethylaminopropylacrylamide (DMAPAA), one type of aqueous copolymer having primary and tertiary amino groups was obtained. By the polymerization of three kinds of monomers, DMAAm, AmSt, and 2-[(methacryloyloxy)ethyl] trimethylammoniumchloride (METAC), another type of aqueous copolymer having primary and quaternary ammonium groups was also obtained. Two more types of copolymers were synthesized by copolymerization of -acryloxy-ω-methoxy-poly(ethylene glycol) (a-PEG) with the above two kinds of monomer mixture. These copolymers were polymerized with terephthaloyldichloride at the water/oil interface to prepare four types of microcapsules containing water, i.e., poly(DMAAm-co-DMAPAA-co-AmSt-alt-terephthalic acid) microcapsules, poly(DMAAm-co-DMAPAA-co-AmSt-co-PEG-alt-terephthalic acid) microcapsules, poly (DMAAm-co-METAC-co-AmSt-alt-terephthalic acid) microcapsules, and poly (DMAAm-co-METAC-co-AmSt-co-PEG-alt-terephthalic acid) microcapsules, which will be abbreviated to MC 1, MC 2, MC 3, and MC 4, respectively. It has been predicted that the microcapsule membranes are hydrophilic and soft and have two-sublayer structures from electrophoretic mobility measurements and from the analysis of the data with Ohshima’s electrokinetic theory for soft particles. The outer sublayers of MC 1 and MC 2 are negatively charged and those of MC 3 and 4 are slightly positively charged. Also, the surfaces of MC 1 and MC 2 are harder than those of MC 3 and 4. By PEGylation, the surface charge density in the membranes decreases and the surface becomes softer. It has been found that the membrane of red blood cells (RBC) is also soft and is composed of two-sublayers, the outer sublayer of which is negatively charged and the inner one is positively charged. The interaction of four types of microcapsules with RBC has been studied. It was found that microcapsules with soft surfaces (MC 3 and MC 4) do not interact with RBC, even though the microcapsule surfaces are positively charged and the surface of RBC is negatively charged. On the other hand, microcapsules with negatively charged but harder surfaces (MC 1) interact with RBC to introduce hemolysis. The membrane surface of MC 2, which is obtained by PEGylation of MC 1, becomes softer than that of MC 1 so that the interaction with RBC was weakly suppressed. From these, it was concluded that the dominant factor to control the interaction between synthetic polymer surfaces and biological cell surfaces is not the surface charges carried by the polymer surfaces but the softness of the polymer surfaces.     

Direct synthesis of radioactive carbon labeled fullerences using nuclear reactions

The¹¹C and¹⁴C labeled fullerenes were produced by charged-particle and neutron irradiation, of C₆₀, C₇₀ and their mixture. It was found that a carbon atom of fullerence can be easily exchanged with a radioactive carbon atom produced by a nuclear reaction. The HPLC method was effective for identification and purification of various labeled fullerene families as chemically stable compounds. The radiochemically interesting aspect of the results is not only the production of¹¹C and¹⁴C labeled fullerenes but also the formation of radioactive higher fullerenes which can be simultaneously produced with high yield and in carrier-free form.     

使用相位共轭光精密测量粗糙面物体的振动振幅

提出了一个用于测量粗糙面物体振动振幅的自抽过相位共轭干涉仪,粗糙面反射光的波前失真由相位共轭修复,用这个干涉仪屯一个有粗糙表面的不锈钢片的振动幅分布。     

蓝宝石衬底上RF-MBE生长的GaN中的极性控制和螺旋位错的降低

近年来人们报道了用MBE方法生长GaN的飞速进展,利用RF-MBE方法可以获得高的GAN生长速率和高的电子迁移率.本文讨论了用RF-MBE方法在蓝宝石衬底上生长GaN过程中的极性控制和螺旋位错的降低.在充分氮化的蓝宝石衬底上直接生长GaN,使GaN的极性控制为N-极性,并用高温生长的AlN核化层实现GaN的Ga-极性.对于N-和Ga-极性的GaN这两种情况,高温生长的AlN中间迭层的引入,可以有效地抑制螺旋位错的扩散.位错的降低使GaN的室温电子迁移率得到提高,对于Ga-极性的GaN,其值为332cm²/V·s;而对于N-极性的GaN,其值为688cm²/V·s.     

μSR Study of the Unusual Magnetic Ordering in the Frustrated Antiferromagnet Zn(Cr x Ga1−x )2O4

μSR spectra on the spin frustrating spinel antiferromagnet Zn(Cr _x Ga_1−x )₂O₄ (x=0.9,1.0) have been measured. For x=1.0 compound, both the relaxation rate and the initial asymmetry showed distinct anomalies at the Néel temperature. The magnetic susceptibility for the x=0.9 compound was known to have a faint peak at around 12 K, whose origin was not clear so far. Our μSR study revealed that this temperature is the onset temperature of development of the magnetic correlation accompanied by appreciable spin fluctuations. This revised version was published online in September 2006 with corrections to the Cover Date.     

Dimensional Crossover of Magnetic Transition in Diluted Ising Spin Nets Probed by Muon Spin Relaxation

The magnetic ordering process of Ising spins on diluted square lattice was studied by muon spin relaxation using model compounds Rb₂Co _c Mg_1−c F₄. Muon relaxation shows an anomaly at a remarkably higher temperature T _N ^μSR than the transition temperature determined by neutron Bragg scattering T _N ^ND near the percolation threshold for square lattice (c _p=0.593). The difference between the two temperatures amounts to 50% of T _N ^ND just above c _p. The field cooling effect of DC magnetic susceptibility is appreciable below T _N ^ND while the temperature of the anomaly in AC susceptibility approaches to T _N ^μSR as the frequency is increased. It was concluded that there is a crossover from two-dimensional ordering at T _N ^μSR to three-dimensional ordering at T _N ^ND but the two-dimensional order between T _N ^μSR and T _N ^ND has slow fluctuations due to the fractal structure with a plenty of weak links. This revised version was published online in September 2006 with corrections to the Cover Date.     

Over-doping of Tl2Ba2CuO6 due to charge transfer Tl-(Cu-O)

Superconductivity was observed in La substituted Tl₂Ba₂CuO₆. Both T_c and unit cell dimension, a, increase with increasing La concentration, indicating that an over-doping state in Tl₂Ba₂CuO₆, which was due to charge transfer Tl^3−t-(Cu-O)^p as supported from XPS measurements, was relieved by La substitution for Ba.