Mixtures Of Polar Solvents Research Articles

Polymeric imidazolium ionic liquids as valuable stationary phases in gas chromatography: Chemical synthesis and full characterization

Seven new functionalized polymerizable ionic liquids were chemically prepared, and later applied for the preparation of polymeric stationary phases in gas chromatography. These coated GC columns, which exhibited good thermal stabilities (240–300°C) and very high efficiencies (3120–4200plates/m), have been characterized using the Abraham solvation parameter model. The chromatographic behavior of these polymeric IL columns has been deeply studied observing excellent selectivities in the separation of many organic substances such as alkanes, ketones, alcohols, amines or esters in mixtures of polar and non polar solvents or fragrances. Remarkably, the challenging separation of xylene isomers has been possible using a bis(trifluoromethylsulfonyl)amide based imidazolium IL coated column as a gas chromatography stationary phase.

Distribution of Counterions around Lignosulfonate Macromolecules in Different Polar Solvent Mixtures

Lignosulfonate is a colloidal polyelectrolyte that is obtained as a side product in sulfite pulping. In this work we wanted to study the noncovalent association of the colloids in different solvents, as well as to find out how the charged sulfonate groups are organized on the colloid surface. We studied sodium and rubidium lignosulfonate in water-methanol mixtures and in dimethyl formamide. The number average molecular weights of the Na- and Rb-lignosulfonate fractions were 7600 g/mol and 9100 g/mol, respectively, and the polydispersity index for both was 2. Anomalous small-angle X-ray scattering (ASAXS) was used for determining the distribution of counterions around the Rb-lignosulfonate macromolecules. The scattering curves were fitted with a model constructed from ellipsoids of revolution of different sizes. Counterions were taken into account by deriving an approximative formula for the scattering intensity of the Poisson-Boltzmann diffuse double layer model. The interaction term between the spheroidal particles was estimated using the local monodisperse approximation and the improved Hayter-Penfold structure factor given by the rescaled mean spherical approximation. Effective charge of the polyelectrolyte and the local dielectric constant of the solvent close to the globular polyelectrolyte were followed as a function of the methanol content in the solvent and lignosulfonate concentration. The lignosulfonate macromolecules were found to aggregate noncovalently in water-methanol mixtures with increasing methanol or lignosulfonate content in a specific directional manner. The flat macromolecule aggregates had a nearly constant thickness of 1-1.4 nm, while their diameter grew when counterion association onto the polyelectrolyte increased. These results indicate that the charged groups in lignosulfonate are mostly at the flat surfaces of the colloid, allowing the associated lignosulfonate complexes to grow further at the edges of the complex.

Sub-40 nm polymer dot arrays by self-organized dewetting of electron beam treated ultrathin polymer films

Sub-40 nm size ordered nanodroplet arrays of polystyrene are fabricated by a low dose selective electron beam exposure of an ultrathin polymer film followed by its intensified self organized dewetting under a mixture of water and polar organic solvents. The self organization speeds up patterning and reduces the feature size, both by more than 10 times.

Studies on Hydrogen-Bond Interactions in Ternary Mixtures of Polar Solvents by Dielectric Constant Measurements

The static dielectric constant of equimolar mixtures of formamide+N,N-dimethylformamide and formamide+2-aminoethanol mixed with water, ethyl alcohol, dimethylsulphoxide, and 1,4-dioxane were measured over the entire composition range at 303.15 K. The concentration-dependent non-linear behavior of the dielectric constant of the ternary mixtures confirms the formation of hydrogen-bond interactions between the mixture constituents. The excess dielectric-constant values of the mixtures were determined and discussed in view of the strength of hydrogen-bond interactions and the nature of dipolar ordering. It is found that in ternary mixtures, water acts as a structure-maker and ethyl alcohol, dimethylsulphoxide, and 1,4-dioxane act as structure-breakers for the equimolar formamide+N,N-dimethylformamide and formamide+2-aminoethanol binary structures.

Excited state charge transfer reaction in (mixed solvent + electrolyte) systems: Role of reactant–solvent and reactant–ion interactions

Fluorescence spectroscopic techniques have been used to study the excited state intramolecular charge transfer reaction of 4-(1-azetidinyl)benzonitrile (P4C) in two sets of mixed solvents, (1-propanol + ethyl acetate) and (propylene carbonate + acetonitrile), in the absence and presence of a strong electrolyte, lithium perchlorate. These two sets of mixed solvent systems represent binary solvent mixtures of low and high polarities, respectively. Density, sound velocity and viscosity measurements indicate that these two mixed solvent systems are structurally different. Stronger ion-reactant interaction is evidenced in the mole fraction independence of emission frequencies in electrolyte solutions of low polar binary solvent mixtures. For both these mixtures, the reaction driving force (− ΔG r ) decreases with increase in mole fraction of the relatively less polar solvent component of the mixture. Interestingly, − ΔG r increases significantly on addition of electrolyte in low polar mixtures and exhibits mixture composition dependence but, in contrast, − ΔG r in high polar mixtures does not sense variation in mixture composition in presence of electrolyte. This insensitivity to mixture composition for high polar mixtures is also observed for the measured reaction time constant. In addition, the reaction time constant does not sense the presence of electrolyte in the high polar solvent mixtures. The reaction time constant in low polar mixtures, which becomes faster on addition of electrolyte, lengthens on increasing the mole fraction of the relatively less polar solvent component of the mixture. These observations have been qualitatively explained in terms of the measured solvent reorganization energy and reaction driving force by using expressions from the classical theory of electron transfer reaction.

Block Copolymer Mimetic Self-Assembly of Inorganic Nanoparticles

Emerging strategies for assembling inorganic nanoparticles into ensembles with multiscale organization are establishing a new paradigm for the synthesis of devices and functional materials with applications ranging from drug delivery to photonics. In this work, the solution self-assembly of amphiphilic ionic block copolymers into morphologically tunable aggregates provides the inspiration and design strategy for nanoparticle building blocks with the essential chemical and conformational features of ionic block copolymer chains in aqueous media. We produce inorganic nanoparticles with surface-tethered mixed brushes of hydrophobic and chargeable hydrophilic chains which self-assemble in polar solvent mixtures into unprecedented hierarchical superstructures analogous to known ionic block copolymer aggregates but with complex organizations of nanoparticles in three dimensions. Electrostatic repulsion between hydrophilic chains forces nonequilibrium pathways to variable kinetic structures with internal lamellar organization of nanoparticles; however, decreasing electrostatic interactions through salt or acid addition allows tunable equilibrium assemblies, including supermicelles and bilayer vesicles of nanoparticles, to be formed. The application of ionic block copolymer assembly principles and mechanisms opens a new chemical toolbox for the organization of nanoparticles into functional assemblies.

Preparation and photoluminescence (PL) performance of a nanoweb of P3HT nanofibers with diameters below 100 nm

One-dimensional conjugated polymers can be used to build unperturbed percolation pathways that transport electric charges in the active layer of an organic photovoltaic (OPV) cell. Electrospinning is known to be a facile method for the preparation of 1-D nanofibers, but the diameters of electrospun conjugated polymers have previously been too large for OPV cells. In particular, it has not been possible to electrospin poly(3-hexylthiophene) (P3HT) to produce homogeneous nanofibers. We report a new method for the preparation of homogeneous P3HT nanofibers with diameters less than 100 nm and examine the photoluminescence (PL) properties of these nanofibers as a preliminary test of their use in an OPV cell. Nanofibers of P3HT with diameters less than 100 nm can be successfully and simply electrospun by using the proposed method, in particular without adopting a dual nozzle system, with the aid of an auxiliary polymer, polyethylene oxide (PEO), and a polar solvent mixture consisting of chloroform, dimethylformamide (DMF), and acetic acid. After removal of the auxiliary polymer, a composite film composed of virgin P3HT nanofibers and PCBM was found to exhibit almost 100% PL quenching. These results suggest that the proposed method can be used to produce P3HT nanofibers with an efficient photo-energy conversion structure that is useful in OPV cells.

Computational DFT/CI spectroscopic structural studies of some complexes of benzalbarbituric acid

Via Gaussian 98, calculations have been carried out as B3LYP/6-31G ** basis sets and the predominant tautomers of benzalbarbituric acid (BenzalBA) have been defined taking in consideration the energy of the density functional theory. The electronic transition energies have been calculated for the possible tautomers by the configuration interaction between the ground configuration Eigenfunction and the excited configuration Eigenfunctions explaining the absence of the relative intensity change in the UV spectrum by the heat effect as a result of the coincidence of the transition energies of the possible tautomers. The electronic spectra (UV–visible) were scanned for BenzalBA in different solvents of different polarities to determine the Einstein transition probabilities, dipole strengths, oscillator strengths, lifetime of the excited states and extinction coefficients. The hydrogen bonding and the orientation energy of the polar solvent molecules toward BenzalBA molecule were determined from the spectral studies in mixtures of polar and non-polar solvents. Some complexes were prepared from BenzalBA with some divalent metal ions, i.e. Fe ++, Zn ++ or Cu ++. Their structures have been confirmed by elemental analysis, mass spectra, 1H NMR spectra, atomic absorption spectra and UV–visible spectra. It has been concluded that the structures of the complexes have the C 2h point group symmetry in which two BenzalBA moieties are chelated to any one of the metal ions Fe ++, Zn ++ and Cu ++.

ChemInform Abstract: One‐Pot Synthesis of α‐Alkylidene‐γ‐butyrolacton‐2‐ones (Tetronic Acid Derivatives): Polar Solvent Induces a New Type of γ‐Lactonization.

AbstractStepwise reaction of alkyl acetoacetates such as (I) with primary amines and haloacetyl halides followed by thermal cyclization in a mixture of polar solvents offers an easy entry to E/Z‐mixtures of the title compounds, substructures of biologically active compounds.

ChemInform Abstract: Pyrrolidine‐Catalyzed Condensation of Ethyl Diazoacetate to Aldehydes in Water.

AbstractCondensation of α‐diazo carbonyl compounds with aldehydes in the presence of pyrrolidine proceeds smoothly in water or mixtures of water and polar solvents (methanol, acetonitrile, THF).

Clustering in polar media

Clustering prevails in water-soluble polymers and biological macromolecules. It has also been observed in polar solvent mixtures. The possible causes of clustering are discussed. A systematic investigation of clustering in poly(ethylene oxide)/d-water solutions has been undertaken using the small-angle neutron scattering method. The poly(ethylene oxide) monomer is formed of an oxygen atom and an ethylene group. Using the random phase approximation, partial Flory-Huggins interaction parameters for the three pairs (oxygen/d-water, ethylene/d-water, and oxygen/ethylene) are derived. Results show that the first two (oxygen/d-water and ethylene/d-water) are characterized by a lower critical solution temperature phase behavior (whereby phase separation occurs upon heating), while the third one (oxygen/ethylene) is characterized by an upper critical solution temperature phase diagram (whereby phase separation occurs upon cooling). It is argued that clustering is caused by the increasing repulsive interaction between oxygen and ethylene for decreasing temperature and increasing polymer volume fraction. This leads to increasing attractive interactions between ethylene groups that stick together.

Solvent effects on polymerization of functionalized monomers in presence of alkyl halide/CuBr without a ligand

A modified system of atom transfer radical polymerization was used to perform polymerization of sodium o-methacryloylaminophenylarsonate (o-MAPHA-Na). The reaction was carried out without ligand at 48 °C for 45 h with methyl 2-chloro-propionate (MCP) as the initiator, copper bromide (CuBr) as the metal, and different mixtures of polar solvents, including: dimethylformamide (DMF):H2O (60:40), dimethylsulfoxide (DMSO):H2O (20:80), and DMSO. The 1H NMR spectra showed that MCP was covalently attached as end group of the resulting polymers. Unexpectedly, we found that o- and p-MAPHA-Na could polymerize in the presence of alkyl halides without any initiation method to produce free radicals from alkyl halide. Further experiments suggested that radicals could be generated from the used monomer by initiation methods such ultraviolet radiation of environmental light or temperature. Thus, it was possible that the monomer generated phenyl radicals by breaking its C-As bond. Reactions of o-MAPHA-Na and o-MAPHA with MCP and different ratios of H2O:DMF and H2O:Metanol (MeOH) showed that water was necessary for polymerization to proceed. Finally, we found that o-MAPHA underwent self-initiated polymerization when water was present in the reaction media.

A Model to Study the Behavior of a Polar Polymer in the Mixture of Polar Solvents

The aim of the present work was to purpose a simple model to study the behavior of a polar polymer in a mixture of two polar solvents where the mixed solvents are considered as an effective solvent. This effective solvent interacts with the polymer. The ternary system polymer/solvent1/solvent2 is described by an effective solvent interacting with polymer model (E.S.I.P. model). We propose to calculate the polymer–mixed-solvents interaction parameter on the basis of the solubility parameter concept. New expressions for the second virial coefficient and the preferential adsorption coefficient are given. The proposed model is used to explain the structural transition observed in the system of polyvinylpyrrolidone (PVP)/water/methanol mixture at 25°C and to calculate the preferential adsorption parameter. The enthalpy contribution to the PVP/water interaction parameter was found to dominate the PVP/water interaction parameter. Thus, we consider the dominance of the enthalpy contribution to the polymer–solvent interaction parameter as a fundamental hypothesis when polymer and solvent interact. In addition, according to this hypothesis, the calculated PVP/methanol interaction parameter shows that methanol is a good solvent for PVP at 25°C, as reported in the literature. The E.S.I.P model and the dominance of the enthalpy contribution to the polymer-interaction parameter are used to calculate the polymer–mixed-solvents interaction parameter. Then, the second virial coefficient of the PVP in mixed solvents is deduced, showing a change in the solvent quality in agreement with our previous experimental studies. Finally, the variation of the preferential adsorption parameter versus methanol molar fraction X A is calculated showing different behavior of the polymer versus the mixture composition. The obtained results are in agreement with previous studies by light scattering and rheoviscosimetry of the ternary system PVP/water/methanol at 25°C.

Extraordinary swelling behavior of poly(AMPS) organogel in solvent/DMSO binary mixed media

AbstractThe present article deals with super‐swelling behavior of crosslinked homopolymer of 2‐acrylamido‐2‐methylpropane sulfonic acid, poly(AMPS), in binary mixtures of dimethyl sulfoxide (DMSO) and various polar solvents including water, mono‐, and polyhydric alcohols, and amide solvents such as N‐methyl pyrrolidone. Extraordinary phase transition sequences including a new unusual swelling phenomenon, referred to as “overentrant” swelling, was observed for this polymeric organogel in the solvent/DMSO mixtures. The swelling behaviors were preliminarily explained based on the major interactions involved in the solvation process and dielectric constant of the swelling media. It was established that the “overentrant” region of the swelling profiles was progressed with the increase of dielectric constant of the mixed solvent media. The overentrant region was disappeared with partial replacement of AMPS units with acrylic acid. This was taken as an additional practical evidence for a major role of the sulfonic acid as the main interactive group involved in the solvation process. The unusual phase transitions were also explained via a semiquantitative approach based on the Gutmann's acceptor number and donor number values to emphasis on the key effect of dissociation degree of the sulfonic acid group (as a function of the solvent type and composition) on the swelling behaviors. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Micellization of Alkyl-Propoxy-Ethoxylate Surfactants in Water−Polar Organic Solvent Mixtures

The effects of cosolvents (glycerol, ethanol, and isopropanol) on the self-assembly of novel alkyl-propoxy-ethoxylate surfactants in aqueous solutions have been investigated with a focus on the (i) quantification of solvent effects on the critical micelle concentration (cmc), (ii) free-energy contributions to micellization, (iii) local environment in the micellar solution, and (iv) structure of the micelles. The introduction of the polar organic solvents considered in this work into water decreases cohesive forces in the solvent mixture, resulting in an increase in the solubility of the surfactant molecules. As a result, micelle formation becomes less favorable and the cmc increases. The contribution of the cosolvent to the free energy of micellization is positive, and the data for different mixed solvents collapse onto a single straight line when plotted versus a function of the solubility parameters of the surfactant alkyl chains and the mixed solvents. The behavior of the poly(propylene oxide) part of the alkyl-propoxy-ethoxylate surfactants is hydrophilic, albeit less so in the ethanol-water mixed solvent than in plain water. Pyrene fluorescence emission I(1)/I(3) data suggest that the microenvironment in micellar solutions is affected mainly by the cosolvent concentration, not the surfactant degree of ethoxylation. Small-angle X-ray scattering data for both water and ethanol-water surfactant solutions are consistent with oblate ellipsoid micelles and reveal that the introduction of 20% ethanol decreases the micelle long axis by 10-15%.

Synthesis, Characterization, and Hierarchical Organization of Tungsten Oxide Nanorods: Spreading Driven by Marangoni Flow

Tungsten oxide nanorods were synthesized by a soft chemistry approach using tungsten alkoxide and trioctyl amine and oleic acid as the surfactants. The optical properties of the nanorods were studied. The nanorods were found to be soluble in a wide range of solvents like chloroform, cyclohexane, and so on. Upon solvent evaporation, the nanorods formed hierarchically organized solid state structures. Depending on the solvent used, the nanorods organized in different mesostructures. Moreover, the organization of the nanorods from mixtures of polar and nonpolar solvents was studied. Here, the Marangoni effect resulting from differences in the surface tensions of the two solvents was found to play a role in the organization of the nanorods. Furthermore, dip coating of the nanorod solutions on a mica substrate resulted in the formation of a uniform thin film of the nanorods, which may be useful for a variety of applications such as in electrochromic devices and in organic light emitting devices (OLEDs) using tungsten oxide as a buffer layer.

Polymer-induced ordering and phase separation in ionic surfactants

We present a new method to induce phase separation in solutions of ionic surfactants. In this method, the phase separation is obtained either by addition of polyelectrolytes or nonionic polymers along with inorganic salt. As a result, the system separates into polyelectrolyte-rich (or nonionic polymer-rich) and surfactant-rich phase. Four types of the mixtures were investigated: (i) anionic surfactants and anionic polyelectrolytes, (ii) cationic surfactants and cationic polyelectrolytes, (iii) cationic surfactants and nonionic polymers, and (iv) anionic surfactants and nonionic polymers. We found that the addition of polyelectrolyte with the charge of the same sign as that of surfactant can induce the phase separation in a wide range of surfactant concentrations. The addition of nonionic polymers induces the phase separation only in solutions of cationic surfactants. Moreover, the addition of nonionic polymers induces the phase separation only for relatively high total content of polymer and surfactant in the mixture. We found however that the addition of inorganic salt to the mixture of cationic surfactant and nonionic polymer triggers the phase separation even for a small concentrations of surfactant. In our experiments, water as well as mixtures of water and polar solvents were employed as solvents. Based on the optical microscopy studies we found that the surfactant-rich phase represents hexagonal ordering.

Synthesis, spectroscopic and structural elucidation of 1-butyl-4-[2-(3,5-dimethoxy-4-hydroxyphenyl)ethenyl)]pyridinium chloride tetrahydrate

The novel chloride salt of 1-butyl-4-[2-(4-hydroxyphenyl)ethenyl)]pyridine ( 1), has been synthesized as the tetrahydrate and its structure and properties elucidated in detail spectroscopically, thermally and structurally, using single crystal X-ray diffraction, linear-polarized solid-state IR-spectroscopy, UV-spectroscopy and mass spectrometry. Quantum chemical calculations were performed with a view to supporting and explaining the experimental structural and spectroscopic data. The compound ( 1) crystallizes in triclinic P 1 ¯ space group and its unit cell contains two independent 1-butyl-4-[2-(3,5-dimethoxy4-hydroxyphenyl)ethenyl)]pyridinium] cations, differing with respect to the butyl chain torsion angle for which values of 80.0(9)° and 173.6(3)° are observed. The cations and anions are joined into infinite layers, formed by two different dimers and including solvent molecules. Hydrogen bonds OH⋯OH 2 (2.814 Å), HOH⋯O(CH 3) (2.960 Å), OH⋯Cl (2.967 Å), HOH⋯Cl − (3.034, 3.188, 3.161 and 3.062 Å) and HOH⋯OH 2 (2.772 Å) are observed. For first time in the literature, we are reporting the crystal structure of the dye with the syring-fragment in the molecule. The spectroscopic properties of the novel compound are compared and with those of the corresponding quinoide form ( 2). Both the forms ( 1) and ( 2) are characterized by 21 and 140 nm solvatochromic effects depending of the type of the solvent. The UV-spectroscopic data in solution confirm the formation of classical H-aggregates in polar protic solvent mixture.

Preferential solvation of spherical ions in binary DMSO/benzene mixtures

We consider a new qualitative approach for treating theoretically the solvation of single-atomic ionic solutes in binary mixtures of polar and nonpolar aprotic solvents. It is based on the implicit continuum electrostatic model of the solvent mixture involving distance-dependent dielectric permittivity epsilon(R) (where R is the distance from the ion) and local concentrations C(1)(R) and C(2)(R) of the solvent ingredients. For a given R, the condition for local thermodynamic equilibrium provides the transcendental equation for explicitly establishing the permittivity and concentration profiles. Computations performed with real Cl(-) and model Cl(+) ions as solutes in benzene/DMSO mixtures are compared with the molecular dynamics simulations of the same systems. A significant discrepancy of molecular and continuum results is revealed for the concentration profiles in the close vicinity of the ion boundary, although the general trends are similar. The continuum methodology cannot account for the formation of rigid solvent structures around ions, which is most significant for the case of Cl(+). Such defect, however, proves to become of less importance in calculations of the solvation free energy, which are quite satisfactory for Cl(-) ion. Free energy calculations for Cl(+) are less successful in the range of low DMSO concentration.

Cobalt bis(dicarbollide) ions functionalized by CMPO-like groups attached to boron by short bonds; efficient extraction agents for separation of trivalent f-block elements from highly acidic nuclear waste

New boron substituted cobalta bis(dicarbollide)(1-) ion ( 1) derivatives of formula [(8,8′-(RPhP(O)(CH 2) nC(O)N) < (1,2-C 2B 9H 10) 2-3,3′-Co] − (R = Ph or C 8H 17, n = 1, 3a, 3b; R = Ph, n = 2, 3c), [(8-(Ph 2P(O)CH 2C(O)NR)(1,2-C 2B 9H 10))(1′,2′-C 2B 9H 11)-3,3′-Co] − (R = H, C 2H 5, CH 2C 6H 5, 5a–c) and [(8-( 2RPhP(O)CH 2C(O)N( 1R)CH 2-1,2-C 2B 9H 10))(8′-CH 3O-1′,2′-C 2B 9H 10)-3,3′-Co] − ( 1R = Benzyl, 2R = Ph or C 8H 17, 7a,b) were prepared with the aim to develop a new class of efficient extraction agents for partitioning of polyvalent f-block elements, i.e. lanthanides and actinides from high-level activity nuclear waste. The anionic ligands were characterized by multinuclear NMR spectroscopy and MS, the structures of Cs 3a and the calcium complex of 7a were determined by X-ray diffraction analysis. The crystallographic study of the Cs 3a proved a formation of linear chains in the structure, where the metal cation is coordinated by oxygen atoms of the CMPO terminal groups. The X-ray structure of the Ca 2+ complex of the ionic ligand 7a proved a 1:3 metal to ligand ratio. Presented also is the X-ray structure of the starting ammonium compound 6 used in the synthesis of 7a and 7b. With exception of 5c, these anionic ligands are of high extraction efficiency, the highest being found for 7a in low polar solvent mixture hexyl methyl ketone–dodecane 1:1. These properties qualify some of these derivatives for possible technological applications.