Mechanical anisotropy of regenerated cellulose films in relation to orientations of crystalline and noncrystalline phases

The mechanical anisotropy of regenerated cellulose films is investigated, first, on the basis of the theory of infinitesimal elasticity. Fairly good agreement of calculated with observed results is obtained on the basis of orthogonal anisotropy with respect to the machine direction and the transverse and thickness directions of the films. The shear modulus G₂₃ along the film plane and the Poisson ratio v₃₂ are 1.5 times; 10² kg/mm² and about 0.4, respectively, in the standard dry state. Second, the mechanical anisotropy in three different dry states is analyzed in terms of the degree of biaxial orientation of two kinds of structural units, cellulose II crystallites and noncrystalline chain segments, and their mechanical anisotropy. The calculation for averaging the mechanical anisotropies of these structural units on the basis of the homogeneous strain hypothesis gives results much higher than the experimental data, whereas the calculation on the basis on the homogeneous stress hypothesis gives results rather lower than experiment. As a modification of the two extreme calculations, a different averaging gives considerably better agreement between the calculated and observed results. The mechanical anisotropy in the wet state is further analyzed primarily in terms of the degree of biaxial orientation of noncrystalline chains by a modification of Krigbaum treatment, based on application of the kinetic theory of entropy elasticity for semicrystalline polymers, to anisotropic systems. The calculation gives results, however, much lower than those obtained experimentally, unless the ratio of the end-to-end distance of the noncrystalline chain to its fully stretched length is taken as unusually large. This may be due to underestimation of the contribution of the crystalline phase to terms of the same type as appear in the Krigbaum treatment.     

Graphical representation of the state of orientation of polymer systems

The orientation distribution function for noncrystalline structural units in polymer systems cannot be determined completely from any experimental source; only the second and/or fourth moments of the distribution function, i.e., the second and/or fourth orders of the generalized orientation factors F_lm^j, can be evaluated. It is there-fore necessary to estimate the distribution function from F_2m^j and F_4m^j. In this paper, a graphical representation of the state of orientation is first discussed in terms of plots of F₄₀^j against F₂₀^j for several types of distribution functions for uniaxial orientation. These are three types of extreme concentration of the distribution at particular polar angles θ₀ given by θ₀ = 0, 0<θ₀<π/2, and θ₀ = π/2; five types of rather realistic distributions having single maxima at θ_j = 0, θ₀, π/2 and double maxima at θ_j = 0, π/2, and a single minimum at θ_j = θ₀; and four types of more realistic distributions including Kratky's floating rod model in an affine matrix. Second, estimation of the distribution function for uniaxial orientation from F₄₀^j and F₂₀^j is discussed quantitatively in terms of the mean-square error by three approximation methods: (a) expansion of the distribution function in finite series of spherical harmonics through the fourth order, (b) approximation of the distribution function as a composite of two components, random orientation and a particular orientation distribution given by N_a (cos²θ_j)^a, N_a being a constant, and (c) approximation of the distribution function by N_a (cos²θ_j)^a alone. It is concluded that when the orientation distribution is sharp, estimation by the second method of approximation gives a smaller error than the first.     

Analysis of the component aldehyde and alcohols in borohydride-reduced dialdehydes from hexosamine derivatives

Unlike the dialdehydes formed from neutral monosaccharide residues, the dialdehydes from hexosamine residues are resistant to acidified ethanethiol, leaving the hemiacetal bond intact. However, the borohydride-reduced dialdehydes are readily split into the component aldehyde and alcohols; gas Chromatographic analysis of their derivatives is useful for structural studies of hexosamine-containing carbohydrates. Investigation by these sequential derivatization reactions indicated that anomeric methyl 2-acetamido-2-deoxy-$\text{d}$-glucopyranosides were oxidized in normal Malapradian fashion, whereas 2-acetamido-2-deoxy-$\text{d}$-glucose was over-oxidized. The rate of oxidation of 2-acetamido-D-glucitol was very rapid; the oxidation product can also be analyzed by the direct dithioacetal method (mercaptalation followed by trimethylsilylation).     

Nucleophilic cleavages of esters and ethers with phenyltellurotrimethylsilane

The title tellurosilane $\text{1}$ reacted with esters and ethers in the presence of catalytic zinc iodide under very mild conditions, giving the corresponding products with C-telluration and O-silylation via nucleophilic cleavages of the CO bonds.     

Untersuchung der Mikroheterogenit?t der Kompositionen von Poly?thylen und Polyoxymethylen mittels der R?ntgen-Methode

Ohne Zusammenfassung     

Rheo-optical studies on the deformation mechanism of semicrystalline polymers. XIV. Alpha and beta mechanical dispersions of spherulitic high-density polyethylene and the dynamic orientation distribution function of crystallites

The dynamic tensile deformation mechanism of spherulitic high-density polyethylene was investigated by dynamic x-ray diffraction at various temperatures and frequencies in order to assign the α and β mechanical dispersions explicity. The uniaxial orientation distribution function q(ζ_j,0) of the jth crystal plane and its dynamic response Δq′_j(ζ_j,0) in phase with dynamic strain were observed for the (110), (200), (210) and (020) crystal planes. Then the orientation distribution function w(ζ,0,η) of crystallites (crystal grains) and its dynamic response Δw′(ζ,0,η), also in phase with the dynamic strain, were determined by a mathematical transformation procedure proposed by Roe and Krigbaum on the basis of the Legendre addition theorem. The temperature and frequency dependences of w′(ζ,0,η) were analyzed in terms of the model parameters for dynamic spherulite deformation combining affine orientation of crystal lamellae with several types of preferential reorientation of the crystal grains within the orienting lamellae. The following assignments are made: (i) The α mechanical dispersion must be assigned to the dynamic orientation dispersion of crystal grains within the crystal lamellae, involving two types of preferential rotations of the grains about their own crystal b and a axes. The rotation about the b axis is associated with lamellar detwisting, mostly in the equatorial zone of uniaxially deformed spherulites; the rotation about the a axis is associated with intralamellar shearing, mostly in the polar zone of the spherulites. Thus both rotations are intralamellar grain-boundary phenomena. (ii) The β mechanical dispersion must be assigned to the dynamic orientation dispersion of the crystal lamellae behaving as rigid bodies. It is not accompanied by reorientation of the crystal grains, but is associated with orientation dispersion of noncrystalline material between the lamellae. Thus it is an interlamellar grain-boundary phenomena.     

A rapid modified gas chromatographic assay for esterase activity.

A rapid modified procedure for the gas chromatogrpahic determination of esterase activity was studied. Aliphatic esters such as ethyl n-butyrate, n-propul n-butyrate, n-butyl n-butyrate and n-amyl n-butyrate were used as substrates and acetone was chosen as the most suitable solvent for dissolving the substrates in order to avoid alcoholysis. The enzyme reaction was started in a mixture of 0.03 M phosphate buffer, pH 7.90, containing an adequals, an aliquot of the reaction solutionwas injected directly on to a gas chromatograph and the alcohols produced were separated.