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.     

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.     

Characterization of polymer networks by measurements of the freezing point depression

Based on the phenomenon of freezing point depression of a solvent byT, experimental evidence is presented to show that the distance between the junction points can be calculated fromT. Direct measurements of the temperature-time-curve of the cooling network and the Differential Scanning Calorimetry offer the determination ofT. Except the mean distances ¯d _c in dependence on cross-linking density, swelling degree, and other network parameters, the distribution of the distance between the junction pointsH(d_c) can be determined, which allows conclusions on the course of cross-linking reaction. This paper attempts to give experimental evidence of influences of the breadth ofH(d_c) on application-relevant properties.     

Surface characterization and thermodynamics of adsorption of Sr2+, Ce3+, Sm3+, Gd3+, Th4+, UO 2 2+ on activated charcoal from aqueous solution

Surface parameters of the activated charcoal were measured using precise instrumental techniques for dehydration, carbon content, trace metals impurities, anions, bulk, tap and true densities, surface area, pore volume, porosity and average particle diameter. The adsorption of Sr²⁺, Ce³⁺, Sm³⁺, Gd³⁺, Th⁴⁺ and UO ₂ ²⁺ ions on activated charcoal from aqueous solution was studied as a function of temperature. Thermodynamic parameters such as HH ⁰ and S ⁰ were calculated from the slopes and intercepts of the linear variation of lnK ₁ vs. 1/T, whereK ₃ is obtained from Langmuir equation. The results show endothermic heats of adsorption, but negative free energy values indicate that the adsorption process of metal ions on activated charcoal is favored at high temperature. The value of isosteric heat of adsorption, calculated from the Clausius-Clapeyron equation, shows that the surface of the activated charcoal is heterogeneous with respect to activity. A wavelength dispersive x-ray fluorescence spectrometer was used for measuring the concentration of metal ions.     

Interaction of Na+, K+, Li+ and Ca2+ ions in Tris-HCl buffer substrate with monolayers of phosphatidic acid and homologous phosphatidic acid alkyl esters

The interaction of ions (Na⁺, K⁺, Li⁺, Ca²⁺) with monolayers of phosphatidic acid alkyl esters (alkyl = methyl, ethyl,n-propyl,n-pentyl) were investigated at the air/water interface on Tris-HCl buffer, as well as on the electrolytes containing subphases.Qualitatively it can be stated that there are no considerable interactions between Na⁺ ions in the substrate and the head groups of phosphatidic acid esters in the monolayers. On the whole, the modification of the shape in the /a and v/a isotherms ( ^s = film pressure, v ^s = film potential) of the homologous phosphatidic acid esters as a function of the length of the ester group on the subphase containing NaCl, KCl, and LiCl corresponds to that on Tris-HCl buffer without admixture of electrolytes.On the other hand the strength of interaction between Ca²⁺ ions and the homologous phosphatidic acid esters depends on the length of the ester group. The film-condensing effect of Ca²⁺ ions becomes smaller with increasing length of the ester group.     

Absorption spectra of 2-styryl-4-phenyl-thiazole ethiodides in organic solvents of varying polarities and determination of the formation constant of the charge transfer complex formed

The electronic absorption spectra of some 2-styryl-4-phenyl-thiazole ethiodides are studied in organic solvents of different polarities. The shorter wavelength band appearing in the visible region is assigned to an intramolecular charge transfer (CT)-transition originating from the phenyl moiety to the positively charged hetero ring, while the longer wavelength one is due to an intermolecular CT-transition from the iodide ion to the 2-styryl-4-phenyl-thiazolinium cation. These assignments are based on the nature of the aldehydic residue and effects of solvent, concentration, and temperature on both the position and absorptivity of the CT complex-band. It is concluded that the CT complex formed will be highly solvated inDMF, DMSO, ethanol and methanol relative to in CHCl₃, dioxane and acetone. The formation constant of the CT complex in solutions of different polarities is determined at different temperatures. Furthermore, the thermodynamic parameters H ^o, G ^o and S ^o for complex formation are calculated and discussed.

---

Absorptionsspektren von 2-Styryl-4-phenyl-thiazol-ethiodiden in verschiedenen Lösungsmitteln und Bestimmung der Bildungskonstanten der Charge-Transfer-Komplexe

Zusammenfassung Die Elektronenanregungsspektren einiger substituierter 2-Styryl-4-phenyl-thiazol-ethiodide wurden in einigen Lösungsmitteln unterschiedlicher Polarität untersucht. Die Absorption bei kürzerer Wellenlänge wird einem intramolekularen Charge-Transfer (CT)-Übergang zugeordnet, die langwellige Bande einem intermolekularen CT-Übergang (Jodid—organ. Kation). Die Diskussion erfolgt basierend auf Substitutions-, Lösungsmittel-, Konzentrations-, und Temperatur-Effekten. Die Komplexbildungskonstanten und die thermodynamischen Parameter H ^o, G ^o und S ^o werden angegeben.

     

Polypeptides mixed monolayers: collapse mechanism

The mechanism of the collapse process of monolayers of poly-L-alanine and of its mixtures with poly--methyl-L-glutamate was studied at the water/air interface at temperatures of 15°, 20°, 25°, and 30 °C.From measurements of the collapse surface pressure as a function of molar ratios and from the determination of the collapse kinetics, as well as from ellipsometrical measurements of the thickness of the film, the complete solubility of the components, even in the collapsed phase, was deduced.Furthermore, activation energies and values ofG*,H*, andS* in relationship to the kinetics of this process were deduced; it was shown that this process is constituted of a first phase of nucleation and of a second phase of growth both for the poly-L-alanine alone and for its mixtures with poly--methyl-L-glutamate.     

Complex formation constants and thermodynamic parameters for La(III) and Y(III)L-serine complexes

Summary The stoichiometric stability constants for La(III) and Y(III)L-serine complexes were determined by potentiometric methods at different ionic strengths adjusted with NaClO₄ and at different temperatures. The overall changes in free energy (G ^o), enthalpy (H ^o), and entropy (S ^o) during the protonation ofL-serine and that accompanying the complex formation with the metal ions have been evaluated.

---

Komplexbildungskonstanten und thermodynamische Parameter für La(III)- und Y(III)-L-Serin-Komplexe

Zusammenfassung Die stöchiometrischen Komplexbildungskonstanten für La(III)- und Y(III)-L-Serin-Komplexe wurden mittels potentiometrischer Methoden bei verschiedenen Ionenstärken (mit NaClO₄ adjustiert) und bei verschiedenen Temperaturen bestimmt. Die Änderungen in der freien Energie (G ^o), Enthalpie (H ^o) und Entropie (S ^o) während der Protonierung und der Komplexbildung mit den Metallionen wurden ermittelt.

     

Network properties of mixtures of protonated and deuterated polyethylene

Mixtures of protonated and deuterated polyethylene were irradiated in the melt. The degree of crystallinity, the degree of crosslinking, as well as the enthalpyH and the melting pointT _M were determined. No significant differences in the degree of crosslinking between protonated and deuterated chains were found. The mass specific entropyS of the uncrosslinked samples remained constant and independent of the deuterium concentration. For the crosslinked samples, a netpoint entropy was postulated. A weaker Van der Waals interaction could explain the decrease in melting temperature by deuteration (for weakly crosslinked samples).     

Molecular properties of acetone and some of its chloroderivatives adsorbed at the surface of water

The relations between the electric surface potential (V) and the surface tension () of aqueous solutions of acetone, chloroacetone, 1,3-dichloroacetone, and their concentration were investigated. The vertical components of dipole moments of the above mentioned compounds were determined using the Helmholtz equation. The calculations were carried out on the basis of surface excess values, which were obtained from surface tension measurements and surface potential changes. Once the vertical component of dipole moments were found and the orientation of adsorbed molecules was assumed, the local dielectric permittivities of the surface monolayer were estimated.     

Thermodynamics of transfer of non-ionic solutes between immiscible liquid phases. I. Transfer of normal alcohols fromn-octane to water at 25°C

A recently developed calorimetric method has been employed to estimate the thermodynamic functions for transfer of 1-propanol, 1-butanol, 1-pentanol, 1-hexanol and 1-heptanol from n-octane to water at 25°C. A linear correlation for G _t ^o as a function of the number of carbon atoms of the alchohol molecule has been found but for H _t ^o and S _t ^o the dependence gave well defined minima.     

Polymer adsorption on fine particles; the effects of particle size and its stability

The effects of particle size on polyacrylamide (PAAm,M _w =59×10⁴, 500×10⁴) adsorption were investigated using a series of well-characterized hematite (-Fe₂O₃) dispersions. The -Fe₂O₃ particles with highly monodisperse and nearly spherical shape ranged in radius from 23 nm to 300 nm. the maximum amount of PAAm adsorption (M _m ) in each system, showed a steady increase with decreasing particle radius and was influenced strongly by particle concentrations in the medium. Furthermore, it was realized that the diameter of -Fe₂O₃ particles after treatment with PAAm under different particle concentrations decreased with increasing particle concentration. The relation between particle concentration in the medium and particle size after treatment was also influenced by the medium pH, i.e., at the medium pH close to the isoelectric point of -Fe₂O₃ particles (pH^o=9.2), the particle size after treatment increased with increasing particle concentration. All these results suggest that in the system of ultra-fine particles, the mixing process between particle-particle and polymerparticle will play an important role on the conformation of adsorbed polymer layer.     

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.     

ViscosityB-Coefficient of ammonium azide and the enthalpy of formation of the azide anion

Recent determination of the standard enthalpy of formation of the ammonium azide _f H ^O (NH N ₃,c) and the assignment of the viscosity B-coefficient for the azide anion, B(N ₃ ^– ,aq), in aqueous solution enable us to estimate the standard enthalpy of formation of the gaseous azide anion, _f H ^O (N ₃ ^–,g , — a thermochemical magnitude in some dispute — to be 192 kJ-mol^–1.     

Equilibrium and non-equilibrium melting of branched polyethylene relating to defect incorporation within crystals

New equilibrium melting point data, for polyethylene containing chain defects, are tested in the light of random copolymer predictions. A simplified expression for the melting point depression of random copolymers containing small amounts of non-crystallizable units is derived. Non-equilibrium melting data for rapidly quenched polyethylene samples are also reported. The fusion enthalpyH(X), and the surface free energy _e for crystals containing defects are evaluated using crystallinity, equilibrium meltingtemperatures and X-ray long period data. It is shown that increasing defect penetration within crystals induces a decrease ofH(X) withX in accordance with theoretical predictions. Finally _e is, similarly, shown to decrease with increasing number of chain defects attached to the crystal surface.     

SCF perturbation theory for unimolecular reactions

A CNDO/2 SCF perturbation theory is presented for interpreting the form of CNDO/2 potential energy surfaces of unimolecular reactions. The analysis is performed by calculating the energy change E arising from a distortion of the molecular geometry along the reaction coordinate. E is decomposed into different perturbational contributions which are appropriate for an interpretation of the perturbation energy E. Moreover, E is resolved into energy parts arising from a single occupied orbital and contributions due to pairwise orbital interactions. In this way one evaluates numerically how the form of the occupied and unoccupied orbitals determines the magnitude of E. If the distortion occurs along a definite symmetry coordinate, group-theoretical arguments can be applied to discuss the magnitude of characteristic components of the perturbation energy. The SCF perturbation theory is used to analyze the isomerization of ethylene, cis-2-butene and cis-2-butenenitrile.This work was partially supported by Nato-Grant No. 1072     

Systematik des Adsorptionsverhaltens homologer aliphatischer Amine an der Grenzfläche Quecksilber/Elektrolyt

Zusammenfassung Dutch die wechselstrompolarographische Kapazitäts-Potential-und Kapazitäts-Zeit-Messungen (E _m = konstant) als Funktion der Aminkonzentration wurden die Adsorptionsisothermen homologer Amine und Amin-Hydrochloride beiT = 25 °C undT = 50 °C experimentell bestimmt.Die Ads orptionsisothermen wurden mittels dimensionsloser Adsorptionstherme nachFrumkin-Damaskin ausgewertet und in Form folgender Adsorptionsparameter diskutiert und verglichen: Attraktionskonstantea; Adsorptionskoeffizientb und freie StandardadsorptionsenthalpieG _A .Der Zuwachs in denG _A -Werten pro CH₂-Gruppe läßt sich zuG _A /CH₂0,3–0,5 kcal. Mol^–1 abschätzen. Bis auf wenige Ausnahmen sind die Adsorptionsparametera, b, undG _A Temperaturfunktionen

---

Summary The adsorption isotherms of homologous amines and some of their hydrochlorides were obtained from capacity-potential- und capacity-time measurements atT = 25 °C andT = 50 °C.From the adsorption isotherms we computed the thermodynamic adsorption parameters according toFrumkin andDamaskin. On the basis of the adsorption parameters attraction constant (a), adsorption coefficient (b) and free standard energy of adsorptionG _A , the results have been discussed und compared.The increase ofG _A per CH₂-group is aboutG _A /CH₂ 0,3 to 0,5 Kcal Mol^–1. In most cases the adsorption parametersa, b andG _A are temperature functions.

---

---

Mit 3 Abbildungen und 1 Tabelle     

Thermodynamic study of solvent extraction of monovalent metal picrates with benzo-18-crown-6 into chloroform

Thermodynamic parameters (H _ex ⁰ and S _ex ⁰ ) for the overall extractions of monovalent metal (Na, K, Rb, and Tl) picrates with benzo-18-crown-6 (B18C6), and those (H _D,L ⁰ and S _D,L ⁰ ) for the distribution of B18C6 were determined between chloroform and water. All the extracted B18C6 complexes were l:1:1 complexes (B18C6:metal ion: picrate anion). The H _ex ⁰ and S _ex ⁰ values for all the metals are negative. Every extraction of the metal picrate with B18C6 is completely enthalpy driven. The H _D,L ⁰ and S _D,L ⁰ values of B18C6 are both positive, and the partition of B18C6 is entirely entropy driven. Enthalpy (H _ex,ip ⁰ ) and entropy changes (S _ex,ip ⁰ ) for ion-pair extractions of B18C6-metal ion complexes with picrate anions were calculated. All the H _ex,ip ⁰ and S _ex,ip ⁰ values are negative, and the ion-pair extractions are completely enthalpy driven.     

Ring-Ring Tautomerism in the Series of Isoxazolidine and Δ2-Isoxazoline Derivatives

We have studied the reaction of 5-hydroxy-3,3,5-trimethylisoxazolidine and 5-hydroxy-3,5-dimethyl-²-isoxazoline with derivatives of thiosemicarbazide and also thiocarbonohydrazine. Both reactions serve as a method for synthesis of the previously unknown 5-thiosemicarbazido(thiocarbonohydrazino)isoxazolidines and -²-isoxazolines. ¹H and ¹³C NMR spectroscopy revealed a tendency of the indicated compounds toward ring-chain and ring-ring tautomeric conversions in solutions involving the 1,2,4-triazolidine, ²-pyrazoline, and 1,2,4,5-tetrazine rings.     

Determination of the surface free energy of modified carbon fibers and its relation to the work of adhesion

Surface free energy of various carbon fibers was determined by tensiometric method in three different procedures. The dispersive _s ^d and the nondispersive _s ^p components were separately determined by contact angle measurements in two-phase system, formamide-n-alkanes. The _s ^p increased by oxidation and decreased by hydrogen reduction, while the _s ^d remained almost constant.The _s ^p value determined from contact angle of water/ethyleneglycol solution tended to become higher. The critical surface free energy was in harmony with the total free energy determined from formamide-n-alkanes system as long as liquids were properly selected. The formation of oxygen-containing functional groups was evidenced by ESCA, and the surface [O]/[C] ratio was related linearly to the surface polarity defined by _s ^p [ _s ^d + _s ^p ] Oxidation in liquid phase resulted in the formation of both hydroxyls and carboxyls, while only hydroxyls were formed in gas phase. The interfacial shear strength of the fiber-epoxy resin could be closely correlated with thermodynamical work of adhesion calculated on the basis of surface free energy and its component.