Masatami Takeda

On the Phase Transition Behaviour of Binary Systems: Various Non-Nematic Solutes in Nematic Solvent (EBBA)

Abstract Phase transition behaviour of the systems of EBBA with methyl alcohol (MeOH), 1.2-dibromo-ethylene (DBE), o-xylene, m-xylene, and p-xylene has been studied. The phase diagrams for each system have been determined by the polarizing microscope. The slopes, βn and Bi, of the nematic and the isotropic phase boundary lines in each system have been qualitatively described by the molecular field treatment proposed by Humphries. The order parameters for both cis-and trans-DBE in EBBA have been obtained from analyses of 1H-NMR spectra. In the nematic phase, they decrease with increase in temperature. In the nematic/isotropic coexisting phase (N/I phase), the order parameter for CIS-DBE is almost independent of temperature. The proton spin-lattice relaxation times (T1) in the MeOH/EBBA system have been measured by a pulse NM R technique. Little temperature dependence of T1 has been found in the N/1 phase region.c

Studies on Polymerization Activities by Soluble Catalysts Based on Compounds of Organotransition Metals and Aluminum Alkyls

Abstract Polymerization activities of the soluble Ziegler-type of catalyst systems, Ti(OR)4-AlEt3, Ti(NEt2)4-AlMe3, and V(NEt2)4-AlEt3, were investigated. In the catalyst system of Ti(OR)4-AlEt3, formation of two types of Ti(III) compounds, i.e., Ti(OR)2Et and its bridged complex with aluminum alkyl, was confirmed by IR and ESR measurements. With the addition of donor molecule to the system, it was found that the polymer yield decreased remarkably and that the bridged complex dissociated into a single or uncomplex Ti(III) paramagnetic species. It has been concluded that the bridged structure of Ti(III) species was responsible for the polymerization activity of styrene. Two reaction products of Ti(NEt2)3Me and Al(NEt2)Me2 were found by NMR spectroscopic observation with the Ti(NEt2)4-AlMe3 catalyst system. From the kinetic study of polymerization of styrene, it was found that Ti(NEt2)3Me is an active species. An anionic mechanism was proposed for the styrene polymerization by Ti(NEt2)3Me. In the polymeriza...

Orientations of 1, 2-Dibromoethylene in Various Nematic Liquid Crystals

Abstract The liquid crystals give generally wide-line NMR spectra, showing little or no fine detail. This is due to the large number of protons in the molecule, resulting in a very large number of overlapping of peaks, and thus unresolved peaks. Both 1H-NMR and ESR method for small amounts of a probe molecule added to a liquid crystal have been used to study orderings and phase transitions in liquid crystals1–6. In the case of the probe molecule is chosen to contain very few protons, its 1H-NMR spectrum will consist of only a few narrow peaks. One of the most useful aspects of the probe spectra is that they provide a sensitive measure of the relative degree of orientation of liquid crystal.

Ultra-High Modulus Polyolefins from Single Crystals

Recently we have shown that single crystal aggregates of ultra-high molecular weight polyethylenes (UHMW-PE), and of polypropylene (UHMW-PP), grown from dilute solutions, exhibit a dramatically high extensibility compared to melt-crystallized forms. The mats of solution-grown crystals for these two polymers have been drawn up to a ratio of 250 for UHMW-PE and 66 for UHMW-PP. Such superdrawn films exhibit extremes of properties including a tensile modulus, up to 220 GPa for the former and 33 GPa for the latter polymer. These values approach the uncertain theoretical maximum modulus reported for the perfect crystal for each of the two polymers. For effective deformation, the first draw step is solid-state extrusion. The choice of original morphology for extrusion draw is of major consequence, with single crystals offering a significant advantage.

Some Solution Properties of Commercial Chlorinated Rubber

市販塩化ゴムをテトラハイドロフラン溶液から水を沈殿剤に使用し分別沈殿法を用いて分別物を作り, その分別物のテトラハイドロフラン溶液の光散乱, 粘度の測定を行ない, Mark-Houwinkの粘度式, [η] =1.98×10-4Mw0.68を得た。次に分別物を種々の溶媒に溶かし, 溶液粘度を測定し, 理想状態での分子鎖の広がりをStockmayer-Fixmanの方法で算出したところ, (r02/M) 1/2の値は溶媒により変化することを見出した。

Studies on Relation between Fundamental Physical Properties and Mechanical Properties in Commercial Polyethylene Resins

市販ポリエチレンの種々の性質を測定したところ低密度ポリエチレングループと高密度ポリエチレングループに分けて記述できることを示した。メルトインデックス, 耐ストレスクラック性, 密度や破断強度は主に固有粘度 (分子量) と相関があり, 他方, 降伏強度や結晶化度は主に密度と相関があることを知った。この研究により新しいポリエチレン, たとえば, 低密度で高分子量, または高密度で低分子量, の製造が期待される。