Poly(styrene-b-2-vinylpyridine-1-oxide) diblock copolymers: 3. Microemulsions in water/propan-2-ol/toluene mixtures

Pseudo-ternary phase diagrams have been constructed for the three-component solvent system (toluene+water+propan-2-ol) containing diblock copolymers of poly(styrene-b-2-vinylpyridine-1-oxide). Microemulsions have been shown to form on the water-rich side of the phase diagram, in the region of the phase boundary without polymer. Dynamic light-scattering experiments have led to droplet size values in the region of 100 nm, with the size depending strongly on the propan-2-ol/water concentration, as well as the amount of solubilised toluene in the core. Viscometry experiments have been carried out to measure polymer aggregation numbers in the microemulsion droplets, and interfacial tension measurements have shown that in the absence of propan-2-ol (effectively a cosurfactant) the limiting value of the oil/water interfacial tension, even an saturation adsorption of the copolymer is 20 mNm^–1. However, addition of propan-2-ol reduces the interfacial tension to the very low values generall commensurate with microemulsion formation.     

Poly(styrene-b-2-vinylpyridine-1-oxide) and poly(dimethylsiloxane-b-2 vinylpyridine-1-oxide) diblock copolymers. 1. Preparation and characterisation

Sequential anionic polymerisation routes have been used to prepare AB diblock copolymers, where A is either polystyrene or polydimethylsiloxane, and B is poly(2-vinylpyridine-1-oxide). The latter block, which is water-soluble, was obtained from the oxidation of poly(2-vinylpyridine) using peroxyacetic acid (giving 100% yield).The resultant diblock copolymers were characterised by gel-permeation chromatography, proton nuclear magnetic resonance and gravimetric microanalysis to give relative block lengths and polydispersity indices. For both types of block copolymersM _w /M _n values <1.25 could be readily obtained under carefully controlled conditions.     

Spontaneous film formation from a polymer solution

An unusual continuous film formation process of lateral pentyloxy substituted poly(p-phenylene terephthalate)s (s-PPPT) and poly(carbonate) (PC) is observed. A liquid film of polymer solution creeps over the surface of water dropped into the polymer solution. By vaporization of the solvent a solid polymer film is formed on the water surface and can be removed. The driving force for the film formation mechanism is assumed by the reduction of the surface tension of water. Experiments verify this mechanism by increasing the film formation speed using a gas stream, by reducing the formation speed through lowering the surface tension by rinsing agents, and by lowering the solubility of the polymer. As expected, no effects are found by variation of the pH-value of water. Necessary conditions for the film formation process are: good solubility of the polar polymers in organic solvents having a high vapor pressure, complete phase separation, solution density higher than water density, and a surrounding gas phase unsaturated with solvent vapor.The thickness of the mechanically stable films is less than 0.5 m. The films are amorphous by microscopical, FT-IR, x-ray, and DTA investigations.     

Solute-solvent and solvent-solvent interactions in the preferential solvation of 4-[4-(dimethylamino)styryl]-1-methylpyridinium iodide in 24 binary solvent mixtures

The molar transition energy (E(T)) polarity values for the dye 4-[4-(dimethylamino)styryl]-1-methylpyridinium iodide were collected in binary mixtures comprising a hydrogen-bond accepting (HBA) solvent (acetone, acetonitrile, dimethyl sulfoxide (DMSO), and N,N-dimethylformamide (DMF)) and a hydrogen-bond donating (HBD) solvent (water, methanol, ethanol, propan-2-ol, and butan-1-ol). Data referring to mixtures of water with alcohols were also analyzed. These data were used in the study of the preferential solvation of the probe, in terms of both solute-solvent and solvent-solvent interactions. These latter interactions are of importance in explaining the synergistic behavior observed for many mixed solvent systems. All data were successfully fitted to a model based on solvent-exchange equilibria. The E(T) values of the dye dissolved in the solvents show that the position of the solvatochromic absorption band of the dye is dependent on the medium polarity. The solvation of the dye in HBA solvents occurs with a very important contribution from ion-dipole interactions. In HBD solvents, the hydrogen bonding between the dimethylamino group in the dye and the OH group in the solvent plays an important role in the solvation of the dye. The interaction of the hydroxylic solvent with the other component in the mixture can lead to the formation of hydrogen-bonded complexes, which solvate the dye using a lower polar moiety, i.e. alkyl groups in the solvents. The dye has a hydrophobic nature and a dimethylamino group with a minor capability for hydrogen bonding with the medium in comparison with the phenolate group present in Reichardt's pyridiniophenolate. Thus, the probe is able to detect solvent-solvent interactions, which are implicit to the observed synergistic behavior.     

Photochromism of 2-(2,4-dinitrobenzyl)benzimidazole in solution

Spectral and kinetic parameters of photochromic 2-(2,4-dinitrobenzyl)benzimidazole in various solvents were studied by flash photolysis. The absorption band of the photoinduced colored form of 2-(2,4-dinitrobenzyl)benzimidazole shifts red with rise in the relative dielectric constant of the solvent. The rate of bleaching of the photoinduced species in ethanol, propan-2-ol, acetone, acetonitrile, and dimethyl sulfoxide is lower by 2–3 orders of magnitude than in benzene, toluene, and hexane due to formation of intermolecular hydrogen bond with the solvent.     

Stereoselectivity ratios in a simple Diels-Alder reaction in aqueous salt solutions of alcohols

This is the first exhaustive report on the variation of stereoselectivity ratios for a simple Diels-Alder reaction between cyclopentadiene and methyl acrylate. The reaction was carried out in aqueous mixtures of methanol, ethanol, propan-1-ol and butan-1-ol in presence of LiClO₄, LiCl, NaCl, KCl, CaCl₂ and MgCl₂. The endo stereoisomer decreases with the increase in carbon chain length of the alcohol. However, LiClO₄, a salting-in agent in water becomes salting-out in aqueous mixtures of alcohols. The solvent properties, thus can be attuned by adjusting the amount of solvents and salts.     

Thermodynamics of hydrochloric acid in (1-propanol+water) from electromotive-force measurements

The standard electromotive force of the cell: PtH₂(g)|HCl(m) in solvent |AgCl|Ag has been determined at 9 different temperatures ranging from 288.15 to 328.15 K in 20 (propan-1-ol+water) mixtures covering the whole range of solvent composition, by an extrapolation method making use of the extended terms of the Debye-Hückel theory. In solvents of high alcohol content, where the dielectric constant is small, it was necessary to correct for ion-pair formation. The temperature variation of the standard e.m.f. was used to calculate the standard thermodynamic functions for the cell reaction, the primary medium effects of various solvents upon HCl, and the standard quantities for the transfer of HCl from the standard state in water to the standard states in each other solvent. The significance of the transfer functions is discussed in relation to the acid-base strength, as well as the structural features of the solvents.     

Polystyrene(1)/poly(butyl acrylate-methacrylic acid)(2) core-shell emulsion polymers. Part I. Synthesis and colloidal characterization

Polystyrene (PS) (1)/Poly(n-butyl acrylate (BA)-methacrylic acid (MAA)) (2) structured particle latexes were prepared by emulsion polymerization using monodisperse polystyrene latex seed (118 nm) and different BA/MAA ratios. Three main aspects have been investigated: i) the polymerization kinetics; ii) the particle morphology as a function of reaction time; iii) the distribution of MAA units between the water phase and the polymer particles.The amount of MAA in the shell copolymer was found to be the main factor controlling the particle shape and morphology. The shape of the structured particles was, generally, non-spherical, and the shape irregularities increased as a particles was, generally, non-spherical, and the shape irregularities increased as a function of reaction time. At the beginning of the second stage reaction, new small particles were observed, which coalesced onto the PS seed as the polymerization proceeded. The distribution of the MAA groups in the latex particles and the serum was analyzed by alkali/back-acid titration, using ionic exchanged latexes. No MAA groups were detected in the latex serum. Due to the lowTg of the BA-MAA copolymers, alkali conductimetric titrations accounted for all the MAA groups on and within the polymer particles. Therefore, for these systems, this method is not only limited to a thin surface layer, as it is often assumed.     

Thermochromism of poly-1-butene gels

Poly-1-butene gels in some solvents of benzene-derivatives show a colouring phenomenon. The colour changes from blue to yellow under irradiation of natural light as the temperature rises from the melting point of the solvent to the sol-gel transition temperature. The colouring phenomenon is due to selective scattering, but not to optical absorption. The apparent characteristics of the phenomenon resemble the thermochromism of cholesteric liquid crystals, although poly-1-butene itself is colourless and has no asymmetric carbons.     

Adhesive effect of high density polyethylene gels on polyethylene moldings

Adhesive effect of polyethylene moldings by use of high density polyethylene gels in organic solvents such as decalin, tetralin, ando-dichlorobenzene was investigated by shearing tests, electron microscope, and DSC measurements. All of the gels showed such a strong adhesive strength over 36 kg/cm² that polyethylene plates of 3 mm in thickness gave rise to necking sufficient for practical use, when heated at 120 °C for 2 h. In particular, the gel in tetralin showed a strong adhesive strength when heated at 110 °C. It was found that adhesive strength increases with the heating temperature; the temperatures at which adhesive strength begins to increase differ depending on the type of polyethylene sample and solvent. It is apparent that polyethylene gels exhibit an adhesive effect when they are heated at higher temperatures than the gel melting temperatures, and that the closer the SP values of solvents used for the gelation are to the molded polyethylene, the stronger the adhesion of the polyethylene molding.     

Studies of solvation in homogeneous and heterogeneous media by electronic spectroscopic method

Solvation characteristics in homogenous (pure and mixed binary solvents) and heterogeneous media (aqueous micelles, beta- and gamma-cyclodextrine solutions) have been studied by monitoring the emission characteristics of a newly synthesised dye. The longest wavelength absorption and emission band of the dye arise due to transition between S(0) and S(1) state. The maximum energy of electronic transition involving intramolecular charge transfer is found to be dependent on both the hydrogen-bond donating ability and the polarity-polarisability in pure solvent. The dipole moment in the S(1) state, as determined by solvatochromic procedure, agrees well with the value obtained by theoretical calculation at the AM1 level. Preferential solvation of the dye by alcohols has been found to occur in ethanol+water, propan-1-ol+water, propan-2-ol+water binary mixtures. In aqueous micellar media the dye molecule is located at the water-micelle interface. The binding constant for the dye-micelle interaction has also been determined. The results have been compared with those for a structurally related symmetrical ketocyanine dye.     

The effects of silica gel (carrier) on the activity (hydrogen yield) of photocatalytic decomposition of water over [pol-Ti(OBu)4 + CH3OH]-complex

A significant effect of pore size has been found on the yield of photolysis of water to hydrogen, ozone (oxidising product) and methane (decomposing product of catalyst or solvent) using [pol-Ti(OBu)₄ + CH₃OH]-complex/SiO₂. The pore structure of silica gel has been found to provide good conditions for forming this type of catalyst.     

Adsorption of fish oil and poly(vinylbutyral) onto aluminum oxide particles studied by light scattering

The effects of added poly(vinylbutyral) (PVB) and oxidized Menhaden fish oil (O-FO) on dilute suspensions of Al₂O₃ in the azeotropic solvent mixture 73/27 Wt.-% trichloroethylene/ethanol were studied by static (SLS) and dynamic light-scattering (DLS). The DLS correlation function consisted of four terms from: 1) interdiffusion of the two solvents, 2) diffusion of Al₂O₃, 3) diffusion of added O-FO and/or PVB, and 4) an induced velocity of particles through the scattering volume due to laser pressure. The amplitude and relaxation time of all terms could be determined. Addition of PVB to the Al₂O₃ suspension resulted in an increase in particle size corresponding to the adsorption of a monolayer of coils. Addition of O-FO to the Al₂O₃ suspension did not produce a significant increase in particle size, indicating either no adsorption or a compact conformation of O-FO molecules on the Al₂O₃ surface.     

Effect of solvent on the kinetics of arylsulfonylation of N-alkylated anilines in a water-propan-2-ol system

The effect of the composition of a water-propan-2-ol solvent on the kinetics of arylsulfonylation of N-ethyl-, N-isopropyl-, and N-butylanilines with 3-nitrobenzenesulfonyl chloride at 298 K was studied. The reaction rate constant increases monotonically with an increase in the water fraction in the solvent from 5 to 30 wt.%. The apparent activation parameters of the reaction of N-butylaniline with 3-nitrobenzenesulfonyl chloride were calculated. No considerable changes in the activation parameters of the reaction were observed on going from pure propan-2-ol to a 10% aqueous solution, which indicates that the mechanism remains unchanged upon solvent change. Propan-2-ol with a water content of 5–30 wt.% can be used in the synthesis of arylsulfonylation products of the amines under study in 98–99% yield. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 937–939, June, 2006.     

Structure and molecular interactions in {ethanol + (propan-1-ol/propan-2-ol)} mixtures at 303.15 K

In view of industrial importance of binary {ethyl alcohol + (propan-1-ol/propan-2-ol)} mixtures, the densities (ρ) and refractive indices (n _D ) of these alkanols mixtures were measured for different compositions at 303.15 K. Molar volumes (V _m) and excess molar volumes (V ^E) of these binary mixtures were calculated from experimental density data of pure solvents and solvents mixtures. The measured refractive index and density data was used to calculate specific refractions (R _D ), molar refractions (R _M) and apparent molar refractions (R _{φ, i} ) of binary mixtures. From mole fraction dependence of apparent molar refractions, the limiting apparent molar refractions (R _{φ, i} ^○ ) of propan-1-ol and propan-2-ol have been determined. The graphical values of R _{φ, i} ^○ for propan-1-ol and propan-2-ol were found to be 9.5664 and 7.405 cm³ mol^?1 respectively. Structural changes, geometrical fittings and molecular interactions in binary mixtures of these alkanols have been discussed.     

Solvent effects on electron transfer reactions. The system iron(III)-phenothiazine in water-alcohol mixtures

Summary The effect of solvent composition (aqueous mixtures of methanol, ethanol, propan-1-ol and propan-2-ol) on the rate constants and activation parameters of the electron transfer between iron(III) and phenothiazine has been investigated. The dependence of the kinetic parameters on the solvent composition is discussed with reference to previously investigated systems.     

Ruthenium-catalyzed transfer hydrogenation of imines by propan-2-ol in benzene

Transfer hydrogenation of a variety of different imines to the corresponding amines by propan-2-ol in benzene catalyzed by [Ru2(CO)4(mu-H)(C4Ph4COHOCC4Ph4)] (1) has been studied. The reaction is highly efficient with turnover frequencies of over 800 per hour, and the product amines were obtained in excellent yields. A remarkable concentration dependence of propan-2-ol was observed when the reaction was run in benzene as cosolvent. An optimum was obtained at 24 equivalents of propan-2-ol to imine, and further increase of the propan-2-ol led to a dramatic decrease in rate. Also the use of polar cosolvents with 24 equivalents of propan-2-ol gave a low rate. It was found that ketimines react faster than aldimines and that electron-donating substituents on the imine increase the rate of the catalytic transfer hydrogenation. Electron-withdrawing substituents decreased the rate. An isomerization was observed with imines having an alpha-hydrogen at the N-alkyl substituent, which is in accordance with a mechanism involving a ruthenium-amine intermediate. It was demonstrated that the ruthenium-amine complex from alpha-methylbenzylamine, corresponding to the postulated intermediate, can replace 1 as catalyst in the transfer hydrogenation of imines. A primary deuterium isotope effect of kCH/CD = 2.7 +/- 0.25 was observed when 2-deuterio-propan-2-ol was used in place of propan-2-ol in the transfer hydrogenation of N-phenyl-(1-phenylethylidene)amine.     

合成(R)-2-异戊氧基丙醇的新方法

以(R)-1,2-丙二醇为原料,经伯醇羟基保护、仲醇O-异戊基取代、脱羟基保护三步反应合成了手性醇(R)-2-异戊氧基丙醇,其结构经NMR和MS确证.     

Physical gels from PVC: molecular structure of pregels and gels by low-angle neutron scattering

In this paper we report on investigations into the short-range molecular structure of pregels (aggregates formed in dilute solutions) and gels as a function of ageing time, temperature and solvent type. In some solvents (diethyl oxalate and bromobenzene) it is found that the structure of the pregels is cylinder-like or ellipsoid-like. The structure is seen to be the same for the gels and the pregels in the investigated range of transfer momentum which leads us to conclude that the gels are probably fiber-like, a statement in agreement with the morphology observed by Yang and Geil. The fiber section is also about the same order of magnitude as that reported by these authors. Also, further evidence is given for the existence of a second type of physical knot, different from those formed by the more syndiotactic sequences. The validity of the molecular structures deduced from these experiments is discussed in the light of macroscopic properties such as compression modulus and swelling.     

Double percolation effect on the electrical conductivity of conductive particles filled polymer blends

Electrical conductivity of carbon black (CB) filled polymer blends which are incompatible with each other was studied as a function of the polymer's blend ratio. Transmission electron microscope (TEM) analysis shows that CB distributes unevenly in each component of a polymer blend. TEM photographs of phase structure of solvent extracted HDPE/PMMA blend and solvent extraction experiments of PMMA/PP blend detect the blend ratio at which the structural continuity of filler rich phase is formed. The electrical conductivity of polymer blends is found to be determined by two factors. One is the concentration of CB in the filler rich phase and the other is the structural continuity of this phase. This double percolation affects the conductivity of conductive particle filled polymer blends.