Singular integrals on the discrete Besov space B1 0,1 (Z)

Summary We show the boundedness of singular integral operators on the discrete Besov space B₁^0,1 (Z). For this purpose, we introduce discrete special molecules on B₁^0,1 (Z).     

Synthesis and characterization of novel liquid‐crystalline copolymers containing thermally stable photochromic groups

To overcome the defects of the thermal instability of azobenzene, a series of novel photochromic, chiral, liquid‐crystalline monomers and polymers were synthesized from (+)‐camphor. The copolymerization of the photochromic monomers with comonomers was carried out. The synthesized monomers and polymers were identified with nuclear magnetic resonance, Fourier transform infrared, and elemental analysis. The composition of the copolymers was estimated with elemental analysis. The specific rotation of the chiral compounds and polymers was evaluated. The thermal stability and phases of the polymers during heating and cooling cycles were studied with differential scanning calorimetry and thermogravimetric analysis. The phases of the polymers were identified with polarized optical microscopy textures and X‐ray diffraction analysis. The distance between the layers of smectic liquid crystals was estimated from the diffraction angles. Photoisomerization of the configurational E/Z structures was investigated with an ultraviolet–visible spectrophotometer with 300‐nm ultraviolet irradiation. The thermal stability of the Z‐structural segment in the polymers was confirmed through the heating of the polymer at 70 °C for over 10 h. The photoisomerization and thermal stability of the C?C bond in the polymeric materials were demonstrated through a series of novel chiral polymers synthesized in this investigation. Both the polarity of the center part and the molecular length at the ends of the molecules were found to be necessary factors for the formation of liquid‐crystalline molecules. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2026–2037, 2007     

Phosphotransacetylase as a key factor in biological production of polyhydroxybutyrate

Phosphotransa cetylase (Pta) catalyzes the reversible conversion of, acetyl-coenzyme A (CoA) to acetyl phosphate. Polyhydroxybutyrate (PHB) synthase and accumulation were compared between a Pta-deficient mutant and the wild-type Escherichia coli, which were transformed with pAE100, coding for 3-ketothiolase, NADPH-dependenta cetoacetyl-CoA reductase, and PHB synthase from Ralstonia eutropha. During the growth period, PHB synthase activity in the Pta-deficient mutant was lower than that in the wild type. PHB accumulation in the Pta-deficient mutant, however, was higher than that in wild-type cells grown in Luria-Bertani (LB) medium containing 1% glucose (high C:N ratio). The Pta-deficient mutant showed PHB accumulation even in LB medium (low C:N ratio), whereas wild-type cells showed no PHB accumulation. These data suggest the activation of PHB synthase by acetyl phosphate that is synthesized by Pta. A decrease in Pta activity probably causes some increase in acetyl-CoA as substrate for the PHB synthesis pathway, resulting in increased PHB accumulation.     

A new approach for controlling birefringent property of cyclic olefin copolymers

This article reports an original method to control the birefringent property of the cyclic olefin copolymer, which has been recently commercialized as a new type of optical resins, via introduction of a third monomer that possesses a negative birefringence into the cyclic olefin copolymer that exhibits an inherently positive birefringence. The mutual compensation between these opposite‐sign birefringences effectively reduced the birefringent magnitude of the corresponding terpolymer. In fact, terpolymerization of norbornene (N), ethylene (E), and styrene (S), in which S exhibits a negative birefringence regarding to the positive birefringence of the NE copolymer was successfully prepared using fluorenylamidodimethyltitanium‐based catalyst, yielding NES terpolymers with controllable birefringent property. Especially, when the S content in the NES terpolymer was controlled at optimum values, it is possible to synthesize a new type of the cyclic olefin copolymer that exhibits an extremely low birefringent magnitude close to zero regardless of high degrees of chain orientation. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7395–7400, 2008     

Dimer effect on fractional polycondensation of poly(p‐oxybenzoyl)

Selective preparation of poly(p‐oxybenzoyl) (POB) crystals was examined from the viewpoint of a dimer effect on fractional polycondensation. Four different copolymerization systems were chosen as the combinations of p‐acetoxybenzoic acid (p‐ABA), m‐acetoxybenzoic acid (m‐ABA), and their dimers. The crystals obtained from the copolymerization of the dimer of p‐ABA (p‐ABAD) and m‐ABA contained only 3.1 mol % of m‐oxybenzoyl moiety even at high content of m‐oxybenzoyl moiety in feed (χ_f) of 40 mol %. p‐Oxybenzoyl homo‐oligomers were more rapidly formed from p‐ABAD in the solution than from p‐ABA, and they were crystallized to form the crystals with segregating co‐oligomers. While co‐oligomers containing more m‐oxybenzoyl moiety were formed in the solution, afterward they were unable to be phase‐separated because of higher miscibility. The further polycondensation proceeded in the precipitated crystal, and finally the POB crystal was selectively formed. Lower polymerization temperature and concentration enhanced the fractionability, and the POB crystals containing less than 1 mol % m‐oxybenzoyl moiety were prepared at χ_f of 30 mol %, 270 °C, and a concentration of 0.5%. The dimer effect on the fractional polycondensation was clearly observed. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1598–1606, 2008     

Initial stage of fiber structure development in the continuous drawing of poly(ethylene terephthalate)

The initial stage of fiber structure development in the continuous neck‐drawing of amorphous poly(ethylene terephthalate) fibers was analyzed by in situ wide‐angle X‐ray diffraction, small‐angle X‐ray scattering, and fiber temperature measurements. The time error of the measurements (<600 μs) was obtained by synchrotron X‐ray source and laser irradiation heating. A highly ordered fibrillar‐shaped two‐dimensional (smectic‐like) structure was found to be formed less than 1 ms after necking. By analyzing its (001′) and (002′) diffractions, the length of the structure 60–70 nm were obtained. A three‐dimensionally ordered triclinic crystal began to form with the vanishing of the structure around 1 ms after necking. The amount and size of the crystal were almost saturated within several milliseconds of necking, during which time a mainly exothermic heat of crystallization was also observed. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 2126–2142, 2008     

Synthesis of aminimides derived from oleic acid: a new family of drag-reducing surfactants

Large-scale syntheses of aminimide surfactants that serve as low temperature drag-reducing agents in ethylene glycol-water mixtures are described. Preliminary drag reduction results are presented and the susceptibility of the surfactants to methanolysis is discussed.