CO2 laser-induced decomposition of propan-2-ol,butan-2-ol,pentan-2-ol,pentan-3-ol,and hexan-2-ol

The pulsed CO₂ laser-induced decompositions of propan-2-ol, butan-2-ol, pentan-2-ol, pentan-3-ol, and hexan-2-ol in the gas phase have been investigated. Like ethanol which we examined previously [1] the absorption cross section of propan-2-ol for pulsed 9R14 radiation increases with pressure at low pressures, an effect attributed to rotational hole-filling. In contrast the absorption cross section of butan-2-ol (10R24) has only a small pressure dependence and those of pentan-2-ol (9R26), pentan-3-ol (10R14), and hexan-2-ol (9P20) show little or no variation with pressure in the range 0.1–5.0 torr. Decomposition products have been investigated at low pressure where the excitation of the alkanols was essentially collision free. The observed products for all the alkanols can be rationalized on the basis of primary dehydration and C? C fission channels, with minor contributions from other molecular eliminations. © 1994 John Wiley & Sons, Inc.     

Poly(styrene-b-2-vinylpyridine-1-oxide) and poly(dimethyl-siloxane-b-2-vinylpyridine-1-oxide) diblock copolymers 2. Micellar solutions in water/propan-2-ol mixtures

Dynamic light scattering and viscometry measurements have been carried out on three AB diblock copolymers in water/propan-2-ol mixtures. The A moieties in each case were poly(2-vinylpyridine-1-oxide) for which both water and propan-2-ol are good solvents. The B Moieties were either polystyrene or polydimethylsiloxane, for which both water and propan-2-ol are poor solvents, but water is the worse solvent. In all cases, the hydrodynamic size of the micelles (assumed spherical) was found to increase with increasing water content in the solvent mixture; the aggregation number was also found to increase. The former finding is in agreement with the theoretical predictions of Munch and Gast, but not the latter.     

The effect of water on the zeta potential of chromium dioxide in tetrahydrofuran

Experiments have been performed to determine the effect of water on dilute suspensions of CrO₂ in tetrahydrofuran (THF). The effect of water in the solvent as well as on the particle surface has been investigated using electrokinetic and dispersion stability measurements. Results of these investigations have shown that the zeta potential of dried CrO₂ (physisorbed water removed) in THF is positive and is dependent on the water content in THF. The zeta potential exhibits a maximum at about 1,800 ppm water. Good correlation also exists between the electrokinetic and dispersion stability measurements.     

Oxidation of higher alcanols by tetra-1-butylammonium permanganate

Summary Oxidations of hexan-1-ol, hexan-2-ol, hexan-3-ol, heptan-1-ol, heptan-2-ol, octan-1-ol, and octan-2-ol with tetra-1-butylammonium permanganate, dissolved in the same alcohols, proceed partly autocatalytically. The rate constants of both catalytic and non-catalytic reactions have been evaluated. Colloidal manganese dioxide, one of the reaction products, has been identified as the catalyst.

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Oxidation höherer Alkanole mit Tetra-1-butylammoniumpermanganat

Zusammenfassung Die Oxidation von 1-Hexanol, 2-Hexanol, 3-Hexanol, 1-Heptanol, 2-Heptanol, 1-Octanol und 2-Octanol durch Tetra-1-butylammoniumpermanganat, gelöst in diesen Alkoholen, verläuft teilweise autokatalytisch. Die Geschwindigkeitskonstanten von katalytischen und nichtkatalytischen Teilreaktionen wurden bestimmt. Das kolloidale Mangandioxid, eines der Reaktionsprodukte, konnte als Katalysator identifiziert werden.

     

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.     

Viscoelastic properties of polyacrylonitrile particles stabilised by a poly-2-vinylpyridine/polytert butylstyrene block copolymer

The viscoelastic properties of a dispersion of polyacrylonitrile particles stabilised by a block copolymer poly-2-vinylpyridine/polytert butylstyrene dispersed in solvesso have been measured as a function of particle concentration and frequency at ambient temperatures. At low volume fraction of particles it was found that the loss modulus of the dispersions was larger than the storage modulus, whilst at volume fractions > 0.40 the storage modulus dominates the rheology. This is attributable to there being a steric repulsion between the particles as a result of an increasing concentration of particles and the resultant reduction in interparticle separation in the dispersion. In addition the observed exponential increase of the storage modulus with increasing particle volume fraction mirrors the exponential increase in force with decreasing surface separation of the same type of polymers adsorbed to mica.     

Mechanism of the grafting of organosilanes on mineral surfaces. IV. Phenylderivatives of sepiolite and poly (organosiloxanes)

Grafting reactions of phenyl groups on silica substrates using as reagents various phenylsilanes with variable distances between the silicon atoms and the aromatic ring by 0, 1, and 2 methylene groups [Si–(CH₂) _n –C₆H₅] were studied. Two different silicates have been selected as source of silica: sepiolite and tetraethyl-orthosilicate (TEOS). Sulfonic- and nitro-derivatives prepared from these phenyl compounds by electrophilic substitution reactions, have been obtained. The mechanism of these processes has been studied in relation to the number of methylene separating groups belonging to the starting reagents. The characterization of such systems has been achieved by XRD,²⁹Si and¹³C NMR/MAS, IR, and laser microprobe mass spectrometry.Parts I, II and III published in this Journal (1978) 256:135–139, (1979) 257:178–181 and (1985) 263:1025–1030     

Generalized rheological characteristic of plastic disperse systems with polymeric and low-molecular dispersion media (matrices)

Analysis of literature data on the flow of polymeric and oligomeric compositions as well as on systems of low viscous dispersion media containing a high-disperse filler (carbon black, silica, high-disperse chalk) has been carried out. As the basic idea, a proposal is made that their viscosity anomaly is due not to the matrix viscosity anomaly, but to the gradual breakdown of the filler structural skeleton with increasing shear stress and shear rate . The viscosity anomaly of those compositions is determined by the zeroshear but not by the apparent matrix viscosity. A general relationship has been found to describe the flow of such systems depending on the zero-shear matrix viscosity values, ₀, their yield stress, _y , and filler volume concentration , whereK=4.9 andn=0.69 are constants.     

Adsorption of polar substances from binary and ternary mixtures on silica gel

The adsorption isotherms of acetone and methyl ethyl ketone from binary and ternary mixtures in benzene and n-heptane on silica gel were measured. The experimental adsorption data are discussed on the basis of changes of the composition of mixed solvent (benzene + n-heptane) in ternary mixtures. It has been found that the different structures of the surface phase correspond to the system investigated. The marked dependence of the adsorption on the solvent character is demonstrated. For benzene and ternary (ketone + benzene + n-heptane) mixtures a mixed character of the surface phase is observed whose composition is determined by competition of liquid components for silica surface as well as its tendency to complex. Bilayer model of the surface phase gives a good representation of the experimental data for binary systems benzene + ketone.     

Experimental and Theoretical Description of Binary Mixtures Containing Monohydric Alcohols

The densities and speeds of sound in the pentan-1-ol + nonan-1-ol, pentan-1-ol + dekan-1-ol, propan-1-ol + hexan-1-ol, and propan-2-ol + hexan-1-ol binary systems have been measured within the whole composition range at 298.15 K. The quantities determined from the measurement data have been plotted as functions of composition. The excess molar volumes have been interpreted on the basis of results of the Symmetrical Extended Real Associated Solution Model (S-ERAS).     

Organogels from water-in-oil microemulsions

A new family of organogels is described. They originate from water-in-oil microemulsions, from which the name microemulsion gels or microemulsion-based gels is derived. Two different types of such gels are presented here, referred to asgelatine gels andlecithin gels, respectively. In the case of gelatine gels, the initial ternary system typically consists of isooctane, AOT (bis 2-ethylhexyl sodiumsuccinate) and water; gelation is induced by solubilization of gelatine in the water microphase above a critical concentration. In the case of lecithin gels no polymeric material is needed. Starting from a reverse micellar solution of lecithin (50–200 mM) in an organic solvent, gelation is induced by the addition of a small amount of water. The molar ratio of water to lecithin typically varies between 1 and 12 for the 50 different solvents investigated to date. These gels are isotropic, thermoreversible and optically transparent.For both microemulsion gels the influence of the concentration of the components on gelation is presented in the form of preliminary phase diagrams.The physico-chemical properties of these organogels were characterized using a variety of techniques such as NMR, DSC, dynamic shear viscosity measurements, and light scattering. Based on these measurements, preliminary models for the structure of these novel systems were developed.It is possible to co-solubilize a variety of reactive molecules in these gels. Therefore, it may be possible to use these organogels for a number of chemical, pharmaceutical, and cosmetic applications.Paper presented at the Workshop on Ringing Gels and Cubic Phases, Bayreuth, October 25–26, 1988.     

Excess molar enthalpies of formamide + some alkan-1-ols (C1-C6) and their correlations at 298.15 K

Excess molar enthalpies, H^E for the binary systems formamide+methanol, + ethanol, + propan-1-ol, + butan-1-ol, + pentan-1-ol, and + hexan-1-ol have been measured at 298.15 K and atmospheric pressure with a Paar 1455 solution calorimeter. All the system present endothermic events and showed maximum positive H^E values around 0.40-0.50 mole fraction of formamide. The H^E values increases in the order: methanol<ethanol<propan-1-ol<butan-1-ol<pentan-1-ol<hexan-1-ol. Experimental showed insolubility of hexan-1-ol in formamide around x≅0.5 mole fraction of formamide. The excess enthalpies of the above mentioned binary systems, were used to discuss interaction between the alkan-1-ols and formamide molecules. The results are interpreted to gain insight into the changes in molecular association equilibria and structural effects in these systems through O···HO hydrogen bonding. The experimental data have been correlated using Redlich-Kister polynomials. In this research work, the thermodynamics models were also tested: NRTL, Wilson models and their parameters were calculated. The correlation of excess enthalpy data in the systems using NRTL model provides good results.     

Flocculation studies of non-aqueous poly(methyl methacrylate) dispersions. II. Stabilization with the diblock copolymer poly (styrene-b-[ethylene-co-propylene])

Well defined non-aqueous dispersions of poly(methyl methacrylate) stabilized by the diblock copolymer poly(styrene-b-[ethylene-co-propylene]) have been studied with a dispersion medium consisting of a binary liquid mixture of n-heptane and n-propanol. Flocculation was induced by adding n-propanol at constant temperature, to find the critical flocculation volume, and by cooling, to find the critical flocculation temperature. Theta conditions for ethylene-propylene copolymer in the same binary liquid mixture were determined using samples obtained by hydrogenating polyisoprene standards. These dispersions just retained stability at theta conditions, with flocculation occurring when the dispersion medium was slightly worse than a theta system for the stabilizing ethylene-propylene chains.     

Displacement processes on hydrophilic/hydrophobic surfaces in methanol-water mixtures

The adsorption from methanol/water and the enthalpy of displacement of methanol by water were studied on K-60 silica gel, on graphitized PRINTEX-80, and onn-alkylammonium vermiculites. The adsorption between the hydrophobized silicate layers was followed by x-ray measurements. The excess isotherms of alkylammonium vermiculites in methanol/water exhibit two maxima corresponding to the two steps of the individual isotherm. The equilibrium constant of the exchange of water by methanol is calculated. For calculating the adsorption capacities and molar adsorption potentials, a new equation is proposed which combines the adsorption excess quantities with free energy and enthalpy functions.     

Determination of the structure factor for concentrated silica dispersions using small angle x-ray scattering. II. Experiment

The structure factor of a number of silica suspensions in cyclohexane, with concentrations ranging from 0.01 to 0.714 gcm^–3, has been determined with small angle x-ray scattering, using a Kratky camera. The experimental structure factor is compared with a theoretical one for which polydispersity effects on the particle scattering factor and on the structure are explicitly taken into account.Analysis of the scattered intensity at a scattering angle=0 shows that the particles in the suspension interact like hard spheres, with a specific hard sphere volume of 0.61 cm³g^–1. A comparison of the experimentally determined structure factor with the structure factor found by a model calculation for a polydisperse system, using the experimental particle size distribution, showed a general agreement. The height of the first maximum agreed well for all concentrations, however its position varied stronger with concentration in the experimental curves. A possible explanation of this effect is given.     

The preparation of monodisperse polyacrylonitrile particles in the presence of AB block co-polymers of poly-2-vinylpyridine/poly tertbutylstyrene

Radical dispersion polymerisation of acrylonitrile in cyclohexane was performed in the presence of the diblock copolymer poly-2-vinylpyridine/poly tertbutylstyrene, giving polymer latex particles stabilised by surface layers of chains of poly tertbutylstyrene. A seeded polymerisation route was employed and the addition of up to a further seven feeds of reactants resulted in the particle growth and the total volume fraction of particles increased to 0.2. The effect of varying the molecular weight of the stabiliser and stabiliser concentration was also investigated. Particle diameter in the range 40–150 nm were obtained depending on the condition of the polymerisation.     

Excess molar enthalpies and heat capacities of dimethyl sulfoxide + seven normal alkanols at 303.15 K and atmospheric pressure

Excess molar enthalpies and heat capacities of binary mixtures containing dimethyl sulfoxide (DMSO) + seven normal alkanols, namely methanol, ethanol, propan-1-ol, butan-1-ol, hexan-1-ol, octan-1-ol, and decan-1-ol, have been determined at 303.15 K and atmospheric pressure. With the exception of the DMSO-methanol system, which shows negative values, all mixtures show positive values of excess molar enthalpies over the whole range of mole fraction, increasing as the number of carbon atoms increases. Heat capacities of pure components have been determined in the range 288.15 < T (K) < 325.15. Molar heat capacities of the mixtures are always positive and decrease as the number of carbon atoms decreases. The results were fitted to the Redlich-Kister polynomial equation. Molecular interactions in the mixtures are interpreted on the basis of the results obtained.     

Ultrasonic measurements and other allied parameters of praseodymium and neodymium palmitates in mixed organic solvents

Ultrasonic measurements on praseodymium and neodymium palmitates were made in a mixture of 60% benzene and 40% dimethyl sulfoxide (V/V), to determine the critical micelle concentration (CMC), soap-solvent interaction, and various acoustic and thermodynamic parameters. The values of the CMC increase with the increase in the size of the cation in the soap molecules. The ultrasonic velocity, specific acoustic impedance, apparent molar compressibility, apparent molar volume and relative association increase while the adiabatic compressibility, intermolecular free length, solvation number, molar sound velocity and available volume decrease with increasing soap concentration.