Orientation of the diphenylene propane unit in stretched polycarbonate from two-dimensional magic-angle-spinning NMR

Two-dimensional magic-angle-spinning (2D-MAS) NMR has been used to measure the orientation parameter, P₂, of the diphenylene propane unit in bisphenol-A polycarbonate oriented by stretching to various extension ratios,, atT=295K andT= 403 K.P ₂ is proportional to the birefringencen, with a maximum birefringencen ₀= 0.189. There is some evidence that the order parameterP ₂ of the DPP units with respect to the chain axis deviates from unity.n ₀ is therefore expected to be different from the birefringence,n ₀ , of perfectly aligned chains of polycarbonate. The experimental results obtained forP ₂() are compared to those predicted by the aggregate model.     

A General Analysis of Field-Based Molecular Similarity Indices

A formalism is presented that incorporates the entirety of all field-based molecular similarity indices of general form S _ij = _ij /h( _ii , _jj ), where the numerator is given by the inner product or overlap of field functions F _i and F _j corresponding to the ith and jth molecules, respectively, and the denominator is given by a suitable mean function of the self-similarities _ii and _jj . This family of similarity indices includes the index initially introduced by Carbó nearly twenty years ago, where h( _ii , _jj ) is taken to be the geometric mean of _ii and _jj , and the well-known indices due to Hodgkin and Richards, and Petke, where h( _ii , _jj ) is taken to be the arithmetic mean and maximum of _ii and _jj , respectively. Two new indices based upon the harmonic mean and minimum of _ii and _jj are also defined, and it is demonstrated that the entire set of field-based similarity indices can be generated from a one-parameter family of functions, called generalized means, through proper choice of the parameter value and suitable limiting procedures. Ordering and rigorous bounds for all of the indices are described as well as a number of inter-relationships among the indices. The generalization of field-based similarity indices, coupled with the relationships among indices that have been developed in the present work, place the basic theory of these indices on a more unified and mathematically rigorous footing that provides a foundation for a better understanding of the quantitative aspects of field-based molecular similarity.     

Diffraction and XPS studies of Cu complexes of intercalated compounds of α-zirconium phosphate. I: Derivation of structural models from powder diffraction data

Reasonable structural models are proposed for the Cu complexes of two intercalated compounds of -Zr(HPO₄)₂·H₂O (-ZrP): one with 1,10-phenanthroline (A) and the other with 2,2-bipyridyl (B). The models are derived from considerations of the unit-cell geometry changes undergone by -ZrP upon insertion of, first, the organic molecules and then copper, in accordance with a set of general criteria of structural analysis called the comparison method.     

Scattering from concentration fluctuations in polymer blends: A monte carlo investigation

The collective scattering function S_coll( ), which describes light (neutron-, x-ray) scattering under wavevector , is obtained from Monte Carlo simulations for a symmetrical polymer mixture. The polymers are modelled by self-avoiding walks ofN _A=N_B=N steps on a simple cubic lattice, where a fraction _V of sites is left vacant, and an attractive energy occurs if two neighboring sites are taken by the same kind of monomer. Spinodal curves are estimated from linear extrapolation of S _coll ^–1 (0) vs./k _B T, whereT is the temperature. Also the single chain structure factor is obtained and the de Gennes random phase approximation (RPA) can thus be tested. Unexpectedly, strong deviations are found if one species is very dilute. The estimation of an effective Flory-Huggins-parameter from scattering data is also discussed.Contributed paper delivered at the Tagung der Deutschen Physikalischen Gesellschaft, Fachausschuß Polymerphysik, Hamburg, March 14–16, 1987.     

Influence of o-benzoquinone nature on initiation of radical polymerization by the o-benzoquinone—tert-amine system

o-Benzoquinones initiate radical polymerization of methacrylates under visible light irradiation in the presence of tertiary amines. Spectral sensitivity of the initiating system coincides with absorption bands of o-benzoquinone attributed to the S(*) (_max 400 nm) and S(n*) (_max 600 nm) transitions. The amine radicals (Am^·) initiating polymerization are generated by the photoreduction of Q in the presence of AmH from the triplet radical pair ³(QH^·, Am^·). The yield of Am^· depends on the difference between the volumes of substituents in the 3 and 6 positions of the quinoid ring and is maximal for symmetrically substituted o-benzoquinones. For a series of derivatives of symmetrical 3,6-di-tert-butyl-o-benzoquinone, the rate of photopolymerization of ,-bis(methacryloyloxyethyleneoxycarbonyloxy)ethyleneoxyethylene (OCM-2) in the presence of N,N-dimethylaniline is determined by the free energy (G _e) of electron transfer from the amine to photoexcited o-benzoquinone. The G _e value includes the energies of oxidation of the amines and reduction of the o-quinones and the energy of the 00 transition of the triplet excited state of o-benzoquinones, which are equal to their redox potentials. The photopolymerization rate is maximal for G _e 0.     

Interaction of CO and O2 on the oxidized surface of polycrystalline palladium

The interaction of CO and O₂ on the oxidized surface of polycrystalline palladium under steady state reaction conditions has been studied. The adsorption of carbon monoxide leads to the appearance of its and states. The state on the surface shifts the temperature dependence of the CO oxidation rate under s.s. conditions by about 200 K.

---

CO O₂ . , CO. CO 200° CO .

     

Formation of ultra-thin films consisting of proteins or polysaccharides and syndiotactic-rich poly-vinyl alcohol mixtures adsorbed at air-solution interface

Ultra-thin films of syndiotactic-rich poly-vinyl alcohol (s-PVA) with several proteins and polysaccharides were prepared by the bubble and frame methods using a mixed dilute aqueous solution (1.5g/dL).The mixed amount of-cyclodextrin (-CD) was the largest among these proteins and polysaccharides giving a weight ratio (-CD/s-PVA) of 1. The ratios of silk fibroin(SF), lysozyme, pepsin, and pectin tos- PVA were 0.58, 0.40, 0.35, and 0.35, respectively. For the-CD/s-PVA and SF/s-PVA blend thin films, the phase separation was observed.     

CPS GL 799

The effect of illumination on transport of sulfonated bisazo direct dyes, CI Direct Yellow 12, and CI Direct Yellow 4, into a cellulose membrane has been studied at various temperatures. Transport of CI Direct Yellow 12, which exhibits photoinduced reversible trans-cis isomerism in aqueous solution into a cellulose membrane, was influenced by illumination. It is likely that the transport was influenced by transisomerization of the photoisomeric dye and the diffusivity was controlled by surface diffusion rather than by pore diffusion under both light and dark conditions.Notations C Concentration of dye in the pores (mol/dm³) - C _E Concentration of electrolyte in the bulk solution (mol/dm³) - C _o Concentration of dye in the bulk solution (mol/dm³) - D _p Pore diffusivity (m²/s) - D _s Surface diffusivity (m²/s) - [M] Mean concentration of dye in membrane (mol/dm³) - [M] _L Local concentration of dye in membrane (=q+ _p C) (mol/dm³) - [M] Mean concentration of dye in membrane (mol/kg) - [M] _L Local concentration of dye in membrane (=q/V+ _p C) (mol/dm³) - F Fractional attainment of equilibrium - l Thickness of membrane (m) - q Concentration of dye adsorbed on pore wall (mol/dm³) - q _o Adsorbed concentration of dye in equilibrium withC _o (mol/dm³) - q Concentration of dye adsorbed on pore wall (mol/kg) - q _o Adsorbed concentration of dye in equilibrium withC _o (mol/kg) - t Time (s) - V Volume of membrane swollen with water per unit dry cellulose (dm³/kg) - x C/C _o - y q/q _o - z Distance that the dye diffused in the membrane (m) - q _o / _o C _o - D _s /D _p - Coefficient of the Freundlich isotherm - _p Pore void fraction - z/l - _p D _p t/l ² - _s D _s t/l ²     

Some rules forS(-2k) dipole sums?

Stieltjes conditions and the ratio test provide necessary but not sufficient conditions onS(-2k) dipole sums. If the dipole sums are accurate the associated [n, n –1] Padé approximant provides a better representation of (), the frequency-dependent dipole polarizability, than a truncated series expression and, in addition, should bound () below. It is shown how constraints on the dipole sums effect the form of the [2,1] Padé approximant and an additional constraint is derived that ensures the analyticity of the approximant on 0 < ₁. There then follows a discussion of the reliability of available literature dipole sum values for small molecules containing H, C, N and O.     

Effect of thick fixed-charge layers on electrostatic interaction — a theoretical approach

The electrostatic interaction pressure of charged surface layers is considered qualitatively and quantitatively. In the case of mutual penetration of the surface layers in addition to Maxwell stress and osmotic resp. hydrostatic pressure an isotropic stress on the fixed charges carrying molecules of the surface layers has to be taken into account. The derivation of the pressure-distance equations is given starting from both thermodynamic/electrostatic and hydrostatic/electrostatic principles. A possible biological significance of the additional stress is discussed emphasizing its role in modifying the structure of surface layer molecules.List of symbols e ₀ elementary charge - k Boltzmann constant - n _i concentration of theith ionic species in the bulk solution - P hydrostatic pressure - P hydrostatic pressure in the bulk volume (× ) - P ^h integration constant, independent on ×:P ^h =P(h) - T absolute temperature - Z _i electrovalence of theith ionic species - thickness of the surface layer - , ₀ relative and absolute permittivities - II(×) osmotic pressure at position × - II osmotic pressure in the bulk solution (× ) - osmotic pressure in the symmetry plane of interacting identical surface layers (electric field strength equals zero) - integration constant, independent on ×: - _e ^h electrostatic component of the disjoining pressure _e ^h = _e (h) - (×) mobile charge density profile (cations and anions of the electrolyte) - (×) fixed charge density profile - ^t(x) total charge density profile ( ^t = +) - ¹(x) fixed charge density profile of one of the two surface layers ( ¹(×) 0 for 0×) - (×) electric potential profile     

Catalase monolayers at the air/water interface I. Reversibilities and irreversibilities

/A-isotherms of catalase monolayers established at the air/water-interface are discussed quantitatively on the basis of molecular data: A relationship between a critical value of the surface pressure, the corresponding molecular area, and the molecular dimension of the molecules at the interface is proposed. It is shown that the unfolding of molecules at the water surface is pH-dependent. For each pH-value there is a distinct degree of unfolding; the molecules keep their globular state at neutral pH. Establishment at the surface of bulk solutions corresponding to globular and partly unfolded states, respectively, catalase molecules keep their original configuration on changing the pH-value of bulk-phase. The monolayers are confirmed to show reversibility with regard to lateral changes of state as well as irreversibility with respect to desorption of molecules.A model is proposed to explain the nature of the critical/A-value occurring in the/A-isotherms: on compression beyond _c, molecular segments are transferred from the surface into the bulkphase via a subsurface layer. From the experiments it is concluded that the surface pressure is determined, not only by the surface itself, but also by this subsurface layer.     

Synthesis and properties of pyrimidinylalkylphosphonic acids

Conclusions Some esters of -(oxodihydro-N-pyrimidinyl)butyl- and -(oxodihydro-N-pyrimidinyi)pentylphosphonic acids, and also some diphenyl -(2,4-dioxo-6-methyl-1,2,3,4-tetrahydro-N-pyrimidinyl)alkyl phosphates, were synthesized.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1397–1401, June, 1975.     

Change of water structure by solvents and polymers Part 4: Albumin-water solutions with acetylsalicylic,hydrochloric and ascorbic acid,lysine- and ammonium chloride and with dextrane and sorbit

Viscosity measurements were made in the temperature range of 10 °–40 °C. The equation= _o exp(B/(T-T _o )) was used with the parameterT ₀ as structure indicator, which is called the limiting temperature. For instance, hydrocarbons, as liquids with quasifree molecules, haveT ₀=O; water as a highly structured liquid hasT ₀= 140–150 K.The polymer investigated was ovalbumin in aqueous solution in a concentration comparable to that of blood. Acetylsalicylic acid produces a protein conformation which breaks the water structure in solution at a pH of within the in vivo region.The question of whether only the acidity determines the water structure breaking properties of the protein is investigated by acidifying albumin-water solutions with hydrochloric acid, lysine chloride and ascorbic acid. All these acids exhibit similar effects. A stronger influence is observed for ammonium chloride. Its interaction with ovalbumin produces a strong structure-breaking effect. The most powerful water structure breaker in albumin-water solutions is dextrane. In a concentration of 10 % it changes the polymer conformation so that the water structure is broken to such an extent that the solution behaves as an almost quasifree liquid withT ₀=O.     

Shear-induced deformation of polystyrene coils in dilute solution from small angle neutron scattering 2. Variation of shear gradient,molecular mass and solvent viscosity

The technique of small angle neutron scattering (SANS) has been used to study the conformation of polystyrene chains in dilute solution under a constant shear gradient. The experiments reveal a distinct anisotropy of the molecular dimensions with regard to the directions parallel and perpendicular to the flow direction on the 2D-multidetector. The deformation ratio of the single polymer chain (R ²/R _iso ² )–1 as a function of the reduced shear gradient=([] · · M _w G)/RT shows a transition from the ideal ²-behaviour for dynamic infinitely flexible coils found at small gradients, to a behaviour with smaller increase at larger. These results are qualitatively consistent with the theory of Cerf for a polymer with finite internal viscosity in a shear gradient. At low(<1), a better agreement with the model of a free-draining coil (Rouse behaviour) than with the Zimm model is observed.     

Phase diagram of the system dihexadecylphosphatidylcholine/dihexadecyl-phosphatidic acid/water/NaOH at pH=14

Differential-scanning-calorimetry, freeze-fracture electron microscopy, and³¹P-NMR spectroscopy were used to study the lyotropic and thermotropic properties of the system dihexadecylphosphatidylcholine/dihexadecylphosphatidic acid/water/ NaOH in dispersion with excess water at pH=14. The phase diagram showed that both phospholipids are demixed nearly completely in the gel phase. The coexistence of theP and theB -phase in the mixtures was pointed out in the freeze-fracture electron micrographs by the ripple structure (P -phase) and by the lamellar structure (B -phase).     

Covalent immobilization of trypsin onto poly(2-hydroxyethyl methacrylate)/polystyrene composite microspheres by cyanogen bromide method and its enzymatic activity

Covalent immobilization of trypsin onto poly(2-hydroxyethyl methacrylate)/ polystyrene composite microspheres, produced by emulsifier-free seeded emulsion polymerization technique, was carried out using the cyanogen bromide method under various conditions. The highest enzymatic activities of the trypsin immobilized in this study against N--benzoyl-L-arginine ethyl ester and N--benzoyl-L-arginine-p-nitroanilide, as low-molecular substrates and casein as a high-molecular substrate, were high, as corresponding to 80%, 85% and 50% of those of free trypsin, respectively.Part C of the series Studies on Suspension and Emulsion.     

Effects of pressure and solvent on the diffusion of aromatic compounds through polymers

The diffusion of six azo and five anthraquinone derivatives through nylon 6, poly(ethylene terephthalate) and secondary cellulose acetate films were studied under high hydrostatic pressures of up to 3000 bar and at temperatures 80–130 °C, by analyzing the diffusion profiles yielded in a stacked multiple film, placed in the solution of the diffusant. It was found that the diffusion coefficient,D, of the diffusant decreased with increasing pressure, giving a linear relationship between InD and the pressure, the slope of which gave the activation volume for the diffusion,V . It was revealedV increased linearly with increasing intrinsic molecular volume of the diffusant,V _w , the slopes being different between the azo and the anthraquinone derivatives. The ratio ofV toV _w (V /V _w ) ranged from 0.13 to 0.93, depending in a sensitive manner on the degree of swelling of the polymer matrix which in turn was varied by the solvent. The overall results could be explained in accordance with the formulation,V _{f, local} +V =V _w , whereV _{f, local} represents the free volume contribution. It was proposed thatV _w is increased by solvation when the solvent is good for the diffusant.     

Electrokinetic study on concentrated suspensions using colloid vibration potential measurements

-potentials of a silica suspension and three types of polystyrene latex suspensions with different surface charge groups were measured, as a function of the particle concentration () in the suspension over a wide range, using the colloid vibration potential (CVP) technique. The concentration dependence of the-potential in silica suspension is explained well by Levine et al.s [1] cell model theory, verifying the applicability of the cell model to the CVP in silica suspension. However, the-potential of latex suspensions ordinarily decreases as the particle concentration increases, even after being corrected by the term of (1-). This tendency is especially noticeable in the systems that have particles with high surface charge densities. Furthermore, the conductivity measurements of these suspensions reveal that the conductivity of these systems, especially in their highly charged state, increases as the particle concentration is increased; opposite in tendency to silica suspensions. These new findings can be explained as follows: on the highly charged surface of a latex particle, a polyelectrolyte-like (hairy) layer is present, which overlaps at some point. This permits interparticle surface conduction and results in the abnormal behavior of CVP in these systems.     

Hydrophile-lipophile balance for 1,3-bis-(Ω-alkoxy-oligooxyethylene)-propan-2-ols

The effective hydrophile content and hydrophile-lipophile balance were determined for l,3-bis-(-alkoxy-oligooxyethylene)-propan-2-ols using retention data of standard alcohols and alkanes determined by gas chromatography. The effect of standard surfactants, polar solutes and polarity parameters on the hydrophile balance was discussed. From the effective hydrophile content (E _e), the HLB values could be estimated asE _e/5.     

Transient photocapacitance study in 4-nitro-4′-aminodiphenyl layers

In 4-nitro-4-aminodiphenyl (NAD) layers the photocapacitance (PhC) transients were investigated. PhC spectral distribution as well as the temperature dependences of time constants (under/_on/or after/_off/illumination) have been measured. The photocapacitance spectral distribution possesses maxima at 350, 500, and 750 nm. It was shown that _on (T) is of exponential form while _off (T) is more complicated. The values of thermal activation energies (0.65±0.05) eV of both time constants coincide. The mechanism of photocapacitance process has been disclosed in NAD layers.