Complex polarizability as used to analyze dielectric relaxation measurements

The effect of representing dielectric properties in terms of the complex polarizability ^c = – i is examined. Loss curves ( and tan ) are shifted towards higher frequencies, revealing the existence of new relaxations and allowing the clarifications of ones already known. We have calculated the shift ratios (at maximum or tan )/ (at maximum or tan ) from the more conventional empirical equations representing the dielectric behavior. Some examples are given.     

Solubilization of oleyl alcohol by pure and mixtures of surfactants

The solubilization behavior of oleyl alcohol by pure and mixtures of surfactants systems have been studied in terms of the maximum additive concentration (MAC), the solubilizing power, and the particle sizes of micelles with or without oleyl alcohol. The surfactants used are amphoteric (N,N-dimethyl-N-lauroyl lysine, DMLL; N,N,N-trimethyl-N-lauroyl lysine, TMLL; N,N-dimethyl-N-(carboxymethyl)-lauryl ammonium, DMCL), anionic (sodium dodecyl sulfate, SDS) and nonionic (alkyl polyoxyethylene ethers).The maximum additive concentration of oleyl alcohol by pure surfactants is larger by nonionic surfactants than by others.For a nonionic surfactant system mixed with DMLL, the mixing effect of surfactant on the increase in the MAC is not recognized. While, for DMLL mixed with SDS, the MAC becomes larger than that by pure surfactants. This may be attributed to the fact that the large micellar size will result in increasing the maximum additive concentration.     

Phase behavior and dynamic properties in mixed systems of anionic and cationic surfactants: lithium perfluorooctanesulfonate/diethanolheptadecafluoro-2-undecanolmethylammonium chloride (DEFUMAC) and lithium dodecyl sulfate/DEFUMAC aqueous mixtures

Two ternary phase diagrams of the cationic perfluorosurfactant diethanolheptadecafluoro-2-undecanolmethylammonium chloride (DEFUMAC) with an anionic perfluorosurfactant lithium perfluorooctanesulfonate (LiFOS) and an anionic hydrocarbon surfactant lithium dodecyl sulfate (LiDS) have been established at 25°C. The total surfactant concentration was less than 20wt%. In a wide mixing region of the LiFOS/DEFUMAC system, a lamellar-type phase,P , was identified by its texture under a polarization microscope and by its x-ray diffraction pattern. Dispersed fragments ofP -phase are present in the dilute solutions in which one surfactant was in excess. The anisotropy of electrical conductivity, flow birefringence, dynamic light scattering, and electric briefringence demonstrate that theP fragments are disk-like with a radius of 0.7 m. The disk-likeP particles are transformed by shear into a spherical aggregate ofL above a critical shear gradient. LiDS/DEFUMAC mixed solution forms dispersed and precipitatedL in the dominant region. Radius and micropolarity of the dispersedL aggregates are decreased as the ratio of LiDS:DEFUMAC approaches 1:1. On the basis of x-ray diffraction measurement the structure of precipitatedL -phase seems to consist of monolayers.     

Adsorption behavior of polymers having phosphoric acid group on γ-Fe2O3 and magnetic characteristics in magnetic coatings

Polymers having phosphoric acid groups were prepared as a model binder for magnetic coatings, and the correlation among the adsorption behavior of the polymers onto-Fe₂O₃ particles and the dispersibility, the orientation, and the packing density of-Fe₂O₃ particles in the magnetic coatings was investigated.PMMA homopolymer molecules hardly adsorbed on-Fe₂O₃, and the interfacial tension at a water/polymer solution (toluene) interface ( _W/T) was scarcely changed compared with a water/toluene interface. Increasing with the content of polymeric phosphoric acid group, the adsorbance of polymer increased and the interfacial tension ( _W/T) decreased. When the content of polymeric phosphoric acid groups was over 0.4 mol%, the adsorbance of polymer and interfacial tension ( _W/T ) remained constant. When these polymers were used as a binder for magnetic tapes, the dispersibility of-Fe₂O₃ in the magnetic coatings was improved, increasing with the content of polymeric phosphoric acid group; however, when the content of phosphoric acid group was over 0.2 mol%, its dispersibility decreased abruptly.Studies on Recording Magnetic Materials and Magnetic Composite. XVIII.     

Photoluminescence Spectra and Crystallization of θ-Al2O3 and α-Al2O3 from AlOOH-Fe(NO3)3 Gels

Diphasic boehmite derived unseeded and seeded (by either -Al₂O₃, -Fe₂O₃, or Fe(NO₃)₃) alumina gel planar monoliths were examined by DTA, XRD and photoluminescence spectroscopy. Luminescence spectra enable sensitive monitoring of the - and -Al₂O₃ crystallization in heat-treated gels due to Cr³⁺ impurity traces. Fe(NO₃)₃ unlike other seeds effectively influences crystallization of both - and -Al₂O₃. The present results are interpreted as prevailing solution or Fe³⁺ ion effect on the crystallization process.     

The effect of segment length and concentration on dielectric properties of polypropyleneoxide-based polyurethanes

Three series of segmented polyurethanes based on MDI, variable chain extender, and polypropylene oxide of MW=1000, 2000, and 3000 were synthesized and their dielectric behavior examined.Dielectric relaxations in the segmented polyurethanes were investigated between –150°C and +150°C in the 100 Hz to 10 kHz range. In general, three transitions, designated as, , and were observed, and ascribed in accordance with calorimetric relaxations to glass transitions of the hard and soft segments, and Shatzki-type motions, respectively. The effect of structure variables such as soft segment size, type of chain extender (ethylene glycol, butane diol, and hexane diol) and soft segment concentration, as well as the effect of interaction of the phases on dielectric properties was discussed. It was found that a certain degree of phase mixing exists in all series, detected by the variation of theT _g of the soft segment with soft segment concentration, contrary to DSC results, which was ascribed to thermal treatment prior to the dielectric measurements. It appears that interfacial polarization becomes important only above the transition temperature.     

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     

Isothermic spherulitic growth and the shape of grain boundaries and growth fronts

We investigate experimentally and theoretically the isothermic growth of two spherulites of different modification into a supercooled isotactic polypropylene film. The faster growing-spherulite grows around the-spherulite, and finally the-spherulite is symmetrically and completely included in. In contrast to literature but in agreement with experimental evidence we find that the grain boundary between the teardropshaped-spherulite and the surrounding-spherulite consists of two parts, where one is always an arc of a logarithmic spiral. This-spherulite ends always in a vertex. Its angle depends on the ratio of the two growth rates only. Behind the vertex an intrinsic--grain boundary exists, degenerating to a channel in bulk material. The growth fron of the-spherulite, which ends on the logarithmic spiral or on the intrinsic grain boundary during growth, consists of an arc of a circle continued by an arc of a logarithmic spirial, too.     

Molecular motions in poly(diethyl siloxane) studied by solid-state29Si NMR

Molecular motions in poly(diethyl siloxane) were studied by solid-state²⁹Si-NMR in the temperature range 180–350 K. In this temperature range two solid phases ₁ and ₂, a mesophase _m, and an amorphous isotropic phase exist. The nature of the chain mobility in the different phases was deduced from the resulting changes in the NMR line-shape governed by anisotropic chemical shift. In the intermediate solid phase ₂ its anisotropy is reduced by 25% compared with the low temperature phase ₁ due to the onset of oscillations around the chain axis and conformational transitions. In the mesophase _m the polymer chain rotates about its long axis yielding an axially symmetric chemical shift tensor opposite in sign to that in the ₁, ₂ phases. The broad transition of the mesophase into the isotropic phase is accompanied by an increase in a narrow Lorentzian line arising from the amorphous phase. The results are compared with previous¹H NMR, Raman-spectroscopy and x-ray measurements.After completion of this work we learnt that PDES has recently also been studied through¹³C-MAS and²⁹Si-NMR by Möller et al. [13].     

Crystallochemical Aspect of Phase Formation in the γ-FeOOH-H2O-NaOH System

Phase transition of metastable -FeOOH into -FeOOH and its chemical transformation into -Fe₂O₃ upon hydrothermal treatment in 0-5 M NaOH solutions at 100-230°C were studied. The regions of formation of the above phases were specified. The probable composition of the crystallizing complexes formed in the solutions and the reactions occurring at their incorporation into various atomically smooth faces of -FeOOH and -Fe₂O₃ were considered.     

Infrared Spectroscopy Analysis of Oxyhydroxides as Intermediate Species in the Formation of Iron Oxides-Silica Xerogels

A detailed infrared spectroscopy analysis in the 2500 to 3800 cm^–1 region has been used to study the formation of species in samples of iron oxides embedded in silica xerogel matrix. We report the presence of , , and forms of iron oxyhydroxides as intermediate species in the formation of -Fe₂O₃, -Fe₂O₃ and -Fe₂O₃ starting from three different iron precursors: iron nitrate, iron chloride and nanometric Fe particles prepared by chemical reduction. Our results show that under thermal dehydration and forms of iron oxyhydroxides transform into hematite and maghemite, respectively, whereas the form transform to the -Fe₂O₃ without going through an intermediate iron oxide phase.     

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.     

Ferromagnetische Phase in Produkten des Kochprozesses von Cd(OH)2/Fe(OH)3

In the system CdO·xFe₂O₃ formed from co-precipitated and boiled hydroxides of Cadmium(II) and Iron(III) the following can be identified by X-ray study: atx0.8-besides the Cd(OH)₂ phase--Fe₂O₃, at 1.5x0.8 fine crystalline -Fe₂O₃ and traces of -Fe₂O₃, at 4>x>1.5 both modifications, i.e. -Fe₂O₃ and -Fe₂O₃, and atx>4 only -Fe₂O₃.The course of specific magnetisation as a function of composition confirms the X-ray findings.

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Mit 3 Abbildungen     

Dynamic shear modulus in the splitting region of poly(alkyl methacrylates)

A systematic study of the dynamic shear modulusG ^*=G+G in three poly(alkyl methacrylates) (PEMA, PnPMA, PnBMA) at frequencies between 0.001 and 500 rad/s is presented. As the splitting frequencies _s are low, aging effects can be observed in the splitting region. There is a systematic shift of the splitting frequency _s to lower values with increasing length of the alkyl side group. In PnBMA a separate shear appearance is observed about two frequency decades below the local mode . This is discussed in terms of the concept of minimal cooperativity. Aging effects are: Shift of the maximum loss frequency to lower values, peak sharpening of the relaxation, and intensity changes of and . These effects are discussed in terms of the sequential aging concept. Aging leads to a pronounced bending of the traces upwards from the equilibrium line in the Arrhenius diagram. These non-equilibrium phenomena are promoted by the small slope m=d(log )/dT of the trace in the splitting region.Dedicated to Prof. E. W. Fischer at the occasion of his 65th Birthday Lieber Herr Fischer, die Hallenser Polymerphysiker danken Ihnen aufrichtig für die warmherzige und effektive Förderung der Polymerwissenschaften im Raum Halle-Merseburg.     

Micropore filling of NO,SO2, NH3, and CO2 onα-FeOOH dispersed activated carbon fibers

Adsorption isotherms of NO, SO₂, NH₃, and CO₂ on-FeOOH dispersed activated carbon fibers at 303 K were examined to determine the role of surface modification in micropore filling. The parameters on micropore structures were obtained from both nitrogen adsorption at 77 K and benzene adsorption at 303 K; both isotherms were of BDDTI type and gave the same micropore volume. The preoxidation conditions of ACF, prior to the deposition of-FeOOH against the NO adsorptivity were examined. The dispersion of-FeOOH on ACF was effective in enhancement of micropore filling, irrespective of the adsorbate molecule. We determined the degree of volume filling for each gas by the use of a DR plot. The modified DR plot for an NO gas, of which the critical temperature was much lower than 303 K, was proposed. The degree of volume filling for various gases was correlated with the deviation of each boiling point from 303 K and with the van der Waalsa constant.     

A new biodegradable polydepsipeptide microsphere for application in drug delivery systems

A sequential polydepsipeptide containing a tripeptide sequence L-alanyl-Lalanyl-ethyl L-glutamyl and an-hydroxy acid L-lactic acid, poly(Ala-Ala-Glu(OEt)-Lac), was synthesized to prepare the microspherical particles by the solvent evaporation process. In this case, the solvents play the most important role for the preparation of polydepsipeptide microspheres and, as an example, when 200 mg of the polydepsipeptide dissolved in 10 ml of 98/2% chloroform/dichloroacetic acid mixture was stirred at 400 rpm and 30 C, the microspherical particles with mean diameter of 58m were formed after pouring into 200 ml of 1% (w/v) poly(vinyl alcohol) solution. 17-Estradiol was incorporated into the particles, and the resulting particles were found to contain 5 mg of drug per 25 mg of the particle. The in vivo release of drug from the microspherical formulation was evaluated by measuring the pharmacological influence on rat prostate. It was found that the sufficient amount of drug, keeping the effective pharmacological influence, is supplied during the first 12-week period, followed by an incomplete supplying of drug intil the implant is perfectly degraded in vivo in the 25th week from the start of implantation.     

Crystalline inclusion compounds of tetrabenzo-18-crown-6 with uncharged organic molecules. Solid-state structure of the nitroethane complex

Diethylaminoethyl (DEAE) groups were introduced into -cyclodextrin (-CD) and -CD. The products, DEAE-CDs with various numbers of substituents, trappedp-nitrophenoxide and 3,4-dinitrophenoxide preferentially over their respective conjugate acids. This caused a decreased pK _a of the guest nitrophenol. Some signals of the proton-NMR of both guest nitrophenol and host DEAE-CD changed upon host-guest interaction. The relation between the number of DEAE groups and the extent of the pK _a decrease, as well as association constants, is discussed.     

Adsorption kinetics with time delay

A theory of adsorption kinetics of solutes onto a solid surface from the solution phase is proposed in which a time delay is introduced into the solute concentration on the surface. Equations governing the adsorption kinetics are similar to those for membrane transport with time delay (Ohshima and Kondo, Biophys. Chem. (1989) 33: 303). It is found that introduction of time delay causes, under certain conditions, overshoot or oscillation in the solute concentrations, both in the solution phase and on the surface. The criterion for oscillation depends on the scaled delay time , the ratio of the possible maximum amount of solutes adsorbed on the surface to the total solute amountR, and the scaled binding constantK. When the number of the binding sites is small, the criterion for oscillation is expressed as >exp(–1), where =(/K) exp().     

Triterpene glycosides from Pulsatilla chinensis

Four triterpene glycosides were isolated from the roots of Pulsatilla chinensis (Bunge) Regel (Ranunculaceae). Two new glycosides, chinensiosides A (1a) and B (2), were identified as 3-O-[-L-rhamnopyranosyl-(12)--L-arabinopyranosyl]-28-O-[-L-rhamnopyranosyl-(14)--D-glucopyranosyl-(16)--D-glucopyranosyl]-3,23-dihydroxylup-20(29)-en-28-oic acid and 3-O-{-L-rhamnopyranosyl-(12)-[-D-glucopyranosyl-(14)]--L-arabinopyranosyl}-28-O-[-L-rhamnopyranosyl-(14)--D-glucopyranosyl-(16)--D-glucopyranosyl]-3,23-dihydroxylup-20(29)-en-28-oic acid. The other two glycosides were identified as previously known hederasaponin C (3) from Hedera helix and glycoside III (4) from Pulsatilla cernua.