The intercalation of a vermiculite by cationic surfactants and its subsequent swelling with organic solvents

We have measured the dimensions of the interlamellar space following intercalation of a vermiculite by a range of cationic surfactants and followed the subsequent swelling of the organoclay compounds with several organic solvents. A single vermiculite (Eucatex) was used with three series of surfactants, N-alkyltrimethylammonium bromides, N,N'-dialkyldimethylammonium bromides, and the gemini cationic surfactants, alpha,omega-bis (N-alkyldimethylammonium) alkanes. In all cases well-defined stoichiometric compounds are obtained and the amount of surfactant intercalating the layer indicates that there are two factors controlling this amount, charge neutralization of the clay and hydrophobic packing. Packing arguments are used to deduce the fraction of non-charge-neutralizing material in the interlamellar space. It is clear that by altering the surfactant charge and structure it is possible to control the degree to which adsorption beyond charge neutralization occurs in these complexes, which is important when the capacity of such complexes to sorb other materials is considered. The general pattern of swelling of the surfactant/vermiculite complex by toluene suggests that the maximum expansion of the intralamellar space is limited by the longest chain in the surfactant. In contrast to earlier results we found that these vermiculites could be swollen by alkanes as well as aromatic solvents. This is attributed to the greater hydrophobicity of the interior of an organoclay formed from a clay of higher charge density.     

Surface modification of poly(dimethylsiloxane) for retarding swelling in organic solvents

A method of alleviating swelling problems of poly(dimethysiloxane) (PDMS) molds in organic solvents is developed that allows repeated use of the molds without deleterious solvent effects. The method involves surface modification of PDMS surface with poly(urethaneacrylate) that results in a partially modified PDMS surface. This modification leads to a significant reduction in the rate of solvent absorption into PDMS such that the swelling can be controlled.     

The effect of chemical modification of the macrocycle on the complex formation between porphyrins and metal salts in organic solvents

The complex formation of β-octaethylporphyrin, β-octaethyl-meso-monophenylporphyrin, β-octaethyl-meso-tetraphenylporphyrin, meso-diphenylporphyrin, meso-triphenylporphyrin, and meso-tetraphenylporphyrin with Zn(II), Cu(II), Co(II), and Mn(II) acetates and chlorides in dimethylformamide, dimethylsulfoxide, pyridine, acetic acid, and a chloroform–methanol 1 : 1 mixture has been studied by means of spectrophotometry. The observed regulations are in line with the concept of chemical reactivity of the N–H bonds in porphyrins of different complexity.     

A fiber optic sensor for water in organic solvents based on polymer swelling

The sensing element is a bead of commercially available anion exchange resin formed by introducing a quaternary ammonium group onto porous crosslinked polystyrene. The diameter of the bead is 20-40% larger in water than in organic solvents investigated in this study including acetone, ethanol, methyl ethyl ketone, 3-pentanone, 4-methyl-2-pentanone and 3-heptanone. The size of the bead varies continuously with the activity of water. In the sensor bead size changes are coupled to movement of a reflecting diaphragm. Movement of the diaphragm changes the intensity of light reflected into an optical fiber. Light intensity is measured as a function of water activity. The results demonstrate that it is possible to sense reversibly and continuously the activity of water in an organic solvent using the phenomenon of the polymer swelling. Problems encountered with cracking of the polymer bead with use and swelling of the diaphragm in the sensor can be addressed by modifying the polymer formulation and changing the sensor design.     

Cross-linking of polyolefins: a study by thermoporosimetry with benzene derivatives as swelling solvents.

The solvents o-, m-, p-xylene, p-dichlorobenzene, 1,2,4-trichlorobenzene, and naphthalene were calibrated as condensates used in the thermoporosimetry technique. Exponential relationships were found connecting the pore radii R(p) (in nm) and the freezing-point depression of the swelling solvent deltaT (in degrees C) on the one hand and the apparent energy of crystallization W(a) (in J cm(-3)) and deltaT on the other hand: R(p) = t exp[-1/(c deltaT)]; W(a) = W0 exp(deltaT/f). Pore- or mesh-size distributions can be derived from differential scanning calorimetry results by using the following equation: dV(p)/dR(p) = k{[cY(T)deltaT2]/[W(a)R(p)]}. All the numerical parameters were determined. Polyethylene and polypropylene samples, cross-linked with high-energy electrons or gamma-rays, were submitted to thermoporosimetry study. Relative mesh-size distributions, which depend on the polymer/solvent pair, were calculated for these polyolefins with o-, m-, and p-xylene as solvent and were found to be in the same sequence as those of their degrees of swelling and the irradiation doses received.     

Interaction of tantalum fluoride with organic solvents

A systematic study on the extraction of tantalum fluoride from various acidic solutions and mixed media has been given using HDEHP, TBP and LA-2 as solvents. The results obtained for these three solvents clarify the ionic behaviour of tantalum. The separation of tantalum from other elements is discussed.     

Spectroscopic investigation of the interaction of methyldichlorosilane with organic solvents

Conclusions The interaction of methyldichlorosilane with organic solvents occurs on account of dipole-dipole interaction (halohydrocarbons), the formation of a SiH ... solvent hydrogen bond with the appearance of a or -complex presumably with a 1:1 composition (cyclohexane, benzene, nitrobenzene, benzonitrile, anisole, cyclohexanone, ethyl acetate, acetone, nitromethane, acetonitrile), and the formation of a SiH ... O hydrogen bond with coordination of a heteroatom of the solvent by the silicon atom and the appearance of a 1:2 complex (diethyl ether).Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2473–2479, November, 1973.     

The swelling of nematic elastomers by nematogenic solvents

The swelling of a nematogenic elastomer by an isotropic solvent was earlier predicted (Macromolecules 25 , 445 (1992)) to be more complex than that of a classical elastomer. We extend here to the swelling by solvents having a nematic-isotropic transition in the pure phase in the region of that of the pure elastomer. The phase diagrams are qualitatively different from the first case, but still with the novel features of a triple point and a gel-gel biphasic gap reported in the initial study. Where the cross-coupling is stronger than the self-couplings we have an azeotropic point.     

Extraction of carpathian menilite shales with organic solvents

Extraction of Carpathian menilite shales with 18 solvents at 20°C was examined.     

Heats of mixing butylacrylate with certain organic solvents

Heats (enthalpies) of mixing binary systems formed by butylacrylate with hexane, benzene, acetonitrile, 1,2-dichloroethane, and acetic acid at 293 K and atmospheric pressure were determined by the calorimetric method.     

The mechanism of the reaction of elementary astatine with organic solvents

The mechanism of the reaction of elementary astatine with benzene, toluene and monochlorobenzene were studied by means of radiogaschromatography. The reaction proceeds in two steps with benzene and toluene. In Step 1 the chemical bond of At₂ is cleaved by the disintegration of either astatine and the remained astatine reacts immediately with solvent. At Step 2 the compound produced at Step 1 is started to decompose by the decay of astatine. But this mechanism could not be applied to the astatine-monochlorobenzene system.     

Effect of quinone derivatives and sulfhydryl compounds on swelling of poly(4-vinylpyridine) gels in organic solvents

Interactions of sulfhydryl compounds and quinone derivatives with poly(4-vinylpyridine) gels have been studied. Adsorption of long-chain sulfhydryl compounds onto gels causes the gel to swell, whereas oxidation of the adsorbed sulfhydryl compound to disulfide by a quinone derivative results in the gel shrinking. The higher the donating ability of the sulfhydryl compound, the stronger its interaction with a quinone derivative and thus the faster the removal from the gels, as revealed by HPLC. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 795–798, 1997     

Sulfation of dextran with chlorosulfonic acid in organic solvents

Solutions of chlorosulfonic acid in dichloroethane and formamide are suggested for incorporation of sulfo groups into macromolecules of polysaccharides. The influence of temperature, reaction duration, and reactant ratio on the yield of sulfated dextran and also the influence of the reaction conditions on hydrolytic stability of the polymer were studied.     

Study on adsorption performance of conjugated microporous polymers for hydrogen and organic solvents: The role of pore volume

A series of homocoupled conjugated microporous polymers (HCMPs) were prepared by cross-coupling polymerization of 1,3,5-triethynylbenzene and 1,4-diethynylbenzene with various monomer molar ratios. Our results show that the molar ratio of monomers has a remarkable influence on the surface area, pore volume, and micropore volume of the as-synthesized HCMP samples. With the increase of molar ratio of 1,3,5-triethynylbenzene to 1,4-diethynylbenzene, the surface area and total pore volume increased while the micropore volume decreased for these HCMP samples. We also investigated the adsorption performance for hydrogen and organic solvents of these HCMP samples. Results obtained from experiments show that the increase of total pore volume (contributed from both mesopore and micropore) of HCMPs would lead to an increase in their adsorption abilities for organic solvents, while hydrogen sorption ability for HCMPs can only be improved by increasing their micropore volume, which may provide useful guidance for the rational design of novel HCMPs with different porosities as absorbent materials for oil/organic solvents or hydrogen storage systems.     

Interaction of Halogenoantimonates with Aromatic Compounds in organic solvents

The interaction of SbCl_nBr_6-n^? (n = 1—6) with various bπ-donors has been investigated by means of UV spectroscopy, conductometry, and polarography. The influence of the bπ-donor structure, of the corresponding cation, the ligands of the antimonates, and the solvent on the behaviour of complex formation is discussed. With increasing ionization potential of the bπ-donor the CT absorption shifts to higher energies. Derivatives of aminobenzene lead to the formation of radical cations. The influence of 18-crown-6 on the radical cation formation is also discussed. With increasing content of bromine in the antimonate the overall acceptor strength increases as well. The influence of the solvent on CT energy depends on both the specific solvation of the ground state of the electron donor-acceptor complex and the dielectric solvation of the excited state of the complex.