Thermotropic liquid crystalline polymers containing five-membered heterocyclic groups VIII. Synthesis, and liquid crystalline and photoluminescent properties of semi-rigid polyesters based on a distyrylbenzene analogue of 1,3,4-thiadiazole

New semi-rigid polyesters composed of the distyrylbenzene analogue of 1,3,4-thiadiazole, 2,5-bis(2-phenylethenyl)-1,3,4-thiadiazole and aliphatic (dodeca-, deca- and octamethylene) chains were prepared by high temperature solution polycondensation; their liquid crystalline (LC) and photoluminescent properties were investigated. Differential scanning calorimetry, polarizing microscopy and powder X-ray diffraction show that the polyesters having both dodeca- and decamethylene chains form a thermotropic smectic C phase and a lyotropic LC phase in trifluoroacetic acid, but the polyester containing octamethylene chains only exhibits a thermotropic smectic C phase. Solution and solid state absorption and fluorescent spectra indicate that all the polyesters in this work display absorption maxima based on the 2,5-bis(2-phenylethenyl)-1,3,4-thiadiazole moiety, emitting blue light in HFIP solutions and bluish-green light in solids; the Stokes shifts are 80.1-80.7 nm in solution and 74.2-87.2 nm in the solid state.     

Monte Carlo wavefunction approach to the dissipative quantum-phase dynamics of two-component Bose-Einstein condensates

We investigate the relaxation effects on the dynamics of two-component dilute gas Bose-Einstein condensates (BEC) with relatively different two-body interactions and Josephson couplings between the two components. Three types of relaxation effects, i.e., one- and three-body losses and a pure phase relaxation caused by elastic two-body collision between condensed and noncondensed atoms, are examined on the dynamical behavior of a macroscopic superposition, i.e., Schr?dinger cat state, of two states with atom-number differences between the two components, which is known to be created by the time evolution in certain parameter regimes. Although three-body losses show a relatively large suppression of the revival behavior of Schr?dinger cat state and the Pegg-Barnett phase-difference distribution between the two components for a small-size Schr?dinger cat state, one- and three-body loss effects are not shown to directly depend on the size of Schr?dinger cat state. In contrast, the pure-phase relaxation effects, causing a reduction of phase-difference distribution and then decaying the Schr?dinger cat state, significantly increase with the increase of the size of Schr?dinger cat state. These features suggest that a detection of damped collapse-revival behavior is highly possible for medium-size Schr?dinger cat states in small-size two-component BECs.     

Effect of molecular size on cooperative dynamics of low mass compounds in polystyrene

We studied the dielectric relaxation behavior of low mass compounds (LMC) mixed in polystyrene (PS). Specifically, LMCs that are used are alkyl‐cyanobenzene (nCBz, n = 0), alkyl‐cyanobiphenyl (nCB, n = 0, 1, 3, 5, and 7), and alkyl‐cyanoterphenyl (nCT, n = 5), where n represents the number of carbon atoms of the normal alkyl groups of the LMCs. Owing to a much larger dipole moment of the cyano group than that of PS, only motions of the LMCs were observed. In a blend of 5CT (5 wt %)/PS, single relaxation process designated as α was observed. On the other hand, in nCB (5 wt %)/PS, partially overlapped two relaxation processes (α and β) were observed in the order of decreasing temperature. We assigned the α process to cooperative motions between the LMC molecules and the PS segments, and the β process to spatially restricted motions of the LMC molecules in the glassy state. In 0CBz (8 wt %)/PS, the α and β processes were observed in distinct temperature regions and the intensity of the α peak was comparable to that of pure PS, indicating that the 0CBz molecules do not move cooperatively with the PS segments. We conclude the existence of two critical sizes (I and II) of LMC in relation to cooperativity: when an LMC molecule is smaller than the size‐I, the motions of the LMCs and PS segments decouple each other, but above the size‐I, they become cooperative. Above the size‐II, the spatially restricted motion (β‐process) of LMC does not occur. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 967–974, 2006     

Effect of lower growth temperature on C incorporation in GeC epilayers on Si(0 0 1) grown by MBE

Effect of lower growth temperature T_s on C incorporation to substitutional sites in Ge_1−xC_x/Si(0 0 1) grown by molecular beam epitaxy was investigated. To enhance the non-equilibrium growth condition, the temperature T_s was lowered from 600°C down to 300°C. The C incorporation into substitutional sites of GeC epilayers was very sensitive to T_s. X-ray diffraction (XRD) measurement indicated that the substitutional C composition x increased with decrease in T_s from 600°C to 400°C. At T_s350°C, the estimation of x by the XRD analysis was impossible because of polycrystallization. The Raman shift measurement enables to estimate x for T_s350°C, as consequently larger x than that grown at T_s=400°C was verified. The enhancement of non-equilibrium growth condition by decreasing T_s was important to increase x.     

Evaluation of in vivo acute immunotoxicity of arsenocholine,a trimethyl arsenic compound in seafood

In this study, we observed the first in vivo acute immunotoxicity of a trimethyl(2‐hydroxyethyl)arsonium cation, namely arsenocholine (AsCho), which is present in marine animals that are ingested daily as seafood in many countries. It has been reported that AsCho has significant acute in vivo toxicity. A high dose of the synthetic pure AsCho was administered to CDF₁ mice intraperitoneally (0.1 g kg^?1 mouse weight) or orally (a total of 10.0 g kg^?1 mouse weight); its effect on the immune organs and immune effector cells was assessed. Administered AsCho, especially via the oral route, showed weak and partial, but significant, in vivo immunotoxicity in mice, although it did not cause any severe acute inflammatory responses. Copyright © 2005 John Wiley & Sons, Ltd.     

Determination of Antimony in Waters by Electrothermal Atomic Absorption Spectrometry with Preconcentration on a Tantalum Wire

 A preconcentration method for antimony in waters involving adsorption on a tantalum wire, followed by electrothermal atomic absorption spectrometry with a tungsten tube atomizer is described. The best pH for the adsorption of antimony was 2. The optimal immersing time was 120 s. Under the optimal conditions, the detection limit for antimony by the tantalum wire preconcentration method was 50 pg/mL (3S/N) and the relative standard deviation was 9.4%. The effects of large amounts of concomitants on the preconcentration of antimony were evaluated. Even though 10³–10⁴ fold excess of matrix elements existed in water, the antimony response was not significantly affected by the matrix elements. The method with preconcentration on a tantalum wire was applied to the determination of antimony in waters and proved to be sensitive, simple, and convenient. This adsorption method can be utilized in in-situ sampling of ultra-trace antimony in environmental samples (water). Furthermore, after sampling it is easy to carry and store the tantalum wire without contamination for a long time. The technique developed was shown to be useful for the determination of Sb in waste waters at the 1–5 μg/L level. Received March 20, 2002; accepted June 26, 2002     

Effects of spinning conditions on the mechanical properties of ultrahigh‐molecular‐weight polyethylene fibers

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 σ_f 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 σ_f which is plotted as a function of T^1/4E^?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     

Investigation of catalyst‐transfer condensation polymerization for synthesis of poly(p‐phenylenevinylene)

Kumada‐Tamao coupling polymerization of 1,4‐dialkoxy‐2‐bromo‐5‐(2‐chloromagnesiovinyl)benzene ( 1 ) and 1,4‐dialkoxy‐2‐(2‐bromovinyl)‐5‐chloromagnesiobenzene ( 2 ) with a Ni catalyst and Suzuki‐Miyaura coupling polymerization of 2‐{2‐[(2,5‐dialkoxy‐4‐iodophenyl)]vinyl}‐4,4,5,5‐tetramethyl‐1,3,2‐dioxaborolane ( 3 ), its bromo counterpart 4 , and 2,5‐dialkoxy‐4‐(2‐bromovinyl)phenylboronic acid ( 5 ) with a Pd initiator were investigated under catalyst‐transfer condensation polymerization conditions for the synthesis of well‐defined poly(p‐phenylenevinylene) (PPV). The Kumada‐Tamao polymerization of vinyl Grignard‐type monomer 1 with Ni(dppp)Cl₂ at room temperature did not proceed, whereas aryl Grignard‐type monomer 2 afforded oligomers of low molecular weight. Matrix‐assisted laser desorption ionization time‐of‐flight (MALDI‐TOF) mass spectra of the polymer obtained from 2 implied that the Grignard end group reacted with tetrahydrofuran to terminate polymerization. On the other hand, Suzuki‐Miyaura polymerization of vinyl boronic acid ester type monomers 3 and 4 and phenylboronic acid type monomer 5 with a Pd initiator and aqueous KOH at ?20 °C to room temperature yielded the corresponding PPV with high molecular weight within a few minutes. However, the molecular weight distribution was broad, and MALDI‐TOF mass spectra showed the peaks of polymers bearing no initiator unit at the chain end, as well as those of polymers with the initiator unit. These results indicated that intermolecular chain transfer of the Pd catalyst occurred. Dehalogenation and disproportionation of the growing end also took place as side reactions. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 2643‐2653     

Targeting Cancer with PCPA‐Drug Conjugates: LSD1 Inhibition‐Triggered Release of 4‐Hydroxytamoxifen

Targeting cancer with small molecule prodrugs should help overcome problems associated with conventional cancer‐targeting methods. Herein, we focused on lysine‐specific demethylase 1 (LSD1) to trigger the controlled release of anticancer drugs in cancer cells, where LSD1 is highly expressed. Conjugates of the LSD1 inhibitor trans‐2‐phenylcyclopropylamine (PCPA) were used as novel prodrugs to selectively release anticancer drugs by LSD1 inhibition. As PCPA‐drug conjugate (PDC) prototypes, we designed PCPA‐tamoxifen conjugates 1 a and 1 b , which released 4‐hydroxytamoxifen in the presence of LSD1 in vitro. Furthermore, 1 a and 1 b inhibited the growth of breast cancer cells by the simultaneous inhibition of LSD1 and the estrogen receptor without exhibiting cytotoxicity toward normal cells. These results demonstrate that PDCs provide a useful prodrug method that may facilitate the selective release of drugs in cancer cells.