Dielectric Constant Of Solvent Research Articles

Effect of Different Dielectric Constant Solvents Addition on PEDOT-PSS Conductive Polymer and its Application

This paper investigates the physical properties of conductive paste which is used for print engineering. The conductivity of poly (3,4-ethylenedioxythiophene) (PEDOT) doped with poly(4-styrenesulfonate) (PSS) containing various organic solvents was measured. The different dielectric constant solvents are isopropanol, N-methyl-2-pyrrolidone, N,N-dimethyl acetamide, dimethyl sulfoxide with different concentration. After drying, they were prepared many kinds of films. It was found that an addition of organic solvent lowered the resistance by two or three orders of magnitude when the concentration is 25wt% , among them the larger dielectric constant solvent has the best surface conductivity, the magnitude is about 7.03×10－1S/cm, and then we blend every two solvents by 25wt% concentration, prepared six blend films. Among them has the best effect, the magnitude is about 1.94×10-1S/cm. All kind of PEDOT/PSS films have been studied using four point probe conductive meter, X-ray diffractometry (XRD), fourier transform infrared (FTIR), thermogravimetric analysis(TGA) in order to discuss the surface conductivity, the crystallinity, the chemical structure and the thermal properties of the PEDOT/PSS film. Conducting PEDOT/PSS-IPA/DMSO solution mix with polymethyl-methacrylate (PMMA) resin to coat hydrophobic fabrics, which can be used for the dissipation of electrostatic charge.

The ab initio study and NBO analysis of the solvent dielectric constant effects and the implicit water molecules on the structural stability of the 1-(6-chloroquinoxalin-2-yl)-2-(4-(trifluoromethyl)-2,6-dinitrophenyl) hydrazine

Ab initio molecular orbital (MO) and density functional theory (DFT) methods were used to analyze the structure and the relative stability of 1-(6-chloroquinoxalin-2-yl)-2-(4-(trifluoromethyl)-2,6-dinitrophenyl) hydrazine in gas phase and the different solvent media. The effects of solvent dielectric constant and the implicit water molecules were investigated on the structural stability and intramolecular interactions. All used methods revealed that by the increase of solvent dielectric constant, the relative stability of the considered compound increase. Hence, the most stable structure is perceived in aqueous solution. Furthermore, natural bond orbital (NBO) analysis demonstrated that in the presence of implicit water molecules, the lone pair electrons of nitrogen have the most contribution in the resonance interactions of the aromatic rings and their stability. These facts may be the probable reasons behind the structural stability of the considered structure in the water solution based on energetic data and NBO analysis at the microscopic level.

Behavior of polyelectrolyte solutions in a wide range of solvent dielectric constant

We exploit the strong temperature dependence of dielectric constant of N-methylformamide to control the strength of electrostatic interactions in polyelectrolyte solutions of sodium polystyrene sulfonate, and investigate the dynamic properties of salt-free solutions over a broad temperature range, from 54 to −58 °C. The traditional fast and slow diffusion processes are observed. The ratio of diffusion coefficients, D s/ D f, increases and the ratio of their amplitudes, A s/ A f, decreases, both by a factor of about two in this temperature range confirming the expected temperature variation with the Bjerrum length.

A DFT study of determination of the reactive sites of the acetylcholine and its agonists: In the gas phase and dielectric medium

AbstractThe reactive behavior of acetylcholine and its agonist molecules have been investigated using B3LYP hybrid density functional method at the 6‐311++G** basis set level, in the gas phase and aqueous phase. The calculations have been performed to obtain optimized geometries, relative reactivities, net atomic charges, HOMO, and LUMO energies. The solvent effect has been analyzed by using the continuum model (IPCM) and, the obtained results have shown that the all molecules have been stabilized more by solvent dielectric constant. For Ach and its analogues, it has been very well known that esteratic site and quaternary ammonium group which have reflected the difference in biological activity have been the two of the most important active site for interactions between molecule and its receptor. The structures of these analogues have provided an essential foundation for subsequent structure‐activity analysis of ligand binding at acetylcholine receptors, neuronal uptake inhibitors and transporters. Molecular modeling predictions will be important initial steps toward the development of novel pharmaceuticals in the fight acetylcholine‐related neurological disorders. This work is therefore expected to facilitate the design and development of new biologically active Ach analogues to treat Ach‐related neurological disorders and, specially is used to qualitative understanding of the reactivity and related properties and, so on can be used to a preselection of new ligands which at the moment is taken essentially from empirical knowledge. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011

Theoretical study of static (Hyper)polarizabilities of twisted intramolecular charge transfer chromophores

AbstractDensity functional theory calculations are performed to study the (hyper)polarizabilities of a series of planar and twisted intramolecular charge transfer molecules (tictoids) with different electron‐donating and electron‐withdrawing groups. Both similarity and difference between the planar and twisted molecules are noted in their (hyper)polarizability variation with respect to substituent and solvent dielectric constant. When compared with dramatic enhancements resulting from geometry twist and solvent effect, substitution to D/A pairs leads to relatively moderate variation in (hyper) polarizability. In addition, tictoids with different substituents may exhibit different solvent effects in their hyperpolarizability magnitudes. Our calculations suggest that the nonlinear optical response of the tictoids could be tuned by appropriately selecting the donor/acceptor pairs and solvents. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2012

Study of the Interaction of Trimethyltin(IV) Chloride with N,N,N’,N’-tetraethylethylenedimanine in Reference to Marine Environmental Pollution

The interaction of trimethyltin(IV) with N,N,N’,N’-tetraethylethylenediamine (Et4en) was investigated potentiometrically. The hydrolysis constants of trimethyltin(IV) species and formation constants of the amine complexes are determined. The formation constant of the complex is high, which may suggest to use Et4en as an antidote for triorganotin(IV) poisoning, the main source of marine environmental pollution. The effect of solvent dielectric constant of the medium and temperature on the complex formation equilibria was investigated.

Solvent effects on SN2 reaction between substituted benzyl chloride and chloride ion

AbstractThe effects of solvent on SN2 reaction between some substituted benzyl chlorides and chloride ion have been investigated by DFT and ab initio methods using the polarizabale continuum model. The activation energies are higher in the solution media relative to the gas phase and grow by the increase in the dielectric constant of solvent. The complexation energies in solution media are smaller than those in the gas phase and reduce with increasing the dielectric constant. The energy data are in good agreement with the geometrical parameters and substituent constants. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2011

SAXS Study of Cytochrome-C Cold Denaturation

We present a study of the cold denaturation of proteins using Small Angle X-Ray Scattering. The size and shape of equine cytochrome-c is determined at varying salt and pH conditions from −25 to 60° C and compared to the two-state Ideal Thermal Protein model of Ghosh and Dill (PNAS 2009). The incorporation of a temperature-dependent pH and solvent dielectric constant is critical to model electrostatic interactions over this broad temperature range and properly predict the observed protein stability from sequence. Under suitable conditions, the protein can be made to increase in size by nearly 9 Angstroms (over 60% of its native radius of gyration) when dropped in temperature from 0 to −25 C. Cold denaturation under these conditions is also verified by monitoring fluorescence from the native tryptophan in this protein. This allows us to compare denaturation monitored at one location inside the protein with global structural changes observed by SAXS.

Ultrafast photoinduced intramolecular charge transfer in push–pull distyryl furan and benzofuran: solvent and molecular structure effect

The excited state deactivation pathways of push-pull distyryl furan and benzofuran derivatives in several organic solvents were investigated in detail by using time-resolved transient absorption and fluorescence spectroscopies, with nano- and femto-second time resolution. Solvent polarity was found to play a key role in determining the efficiencies of fluorescence, intersystem crossing and internal conversion. The triplet yield gradually decreased, while the internal conversion increased upon increasing the solvent dielectric constant. However the fluorescence showed a different solvent polarity effect in the low and high solvent polarity region, with a reversal of the trend of fluorescence properties (quantum yield and lifetime). This fact points to an emitting state of a different nature (smaller and larger dipole moments) in the two cases, as also suggested by the huge fluorosolvatochromism. In fact the ultrafast spectroscopic investigation evidenced the presence of two transients characterized by peculiar spectral shapes assigned to a locally excited (LE) and a charge transfer (CT) state. In the more polar solvents the CT state was the longer lived, fluorescent one and an intramolecular charge transfer process was found to be operative and to become faster (up to ∼200-250 fs) in the higher polarity media. On the contrary, distyrylfuran, which exhibits the same molecular skeleton without the push-pull character showed a similar excited state dynamics in solvents of different polarities.

Comparative study on the gas to solution phase solvation free energies of model combustion flue gas compounds (N~2~, O~2~, CO~2~, H~2~O, SO~2~, and CO) in 178 organic solvents using the IEFPCM-UFF, CPCM, and SMD implicit solvent models at the Gaussian-4 (G4) level of theory

AbstractGas to solution phase Gibbs free energies of solvation at 298.15 K for transfer of six representative combustion flue gas compounds (N~2~, O~2~, CO~2~, H~2~O, SO~2~, and CO) were calculated at the Gaussian-4 (G4) level of theory using the IEFPCM-UFF, CPCM, and SMD implicit solvent models for 178 organic solvents. The IEFPCM-UFF and CPCM models yield similar free energies of solvation for all six compounds in each of the solvents considered, having maximum absolute intra-solvent deviations <1.6 kJ mol^-1^. Substantial free energy of solvation differences were observed between the IEFPCM-UFF/CPCM and SMD models, with maximum absolute intra-solvent deviations up to 45.5 kJ mol^-1^. The IEFPCM-UFF and CPCM models displayed strong free energy of solvation correlations with the solvent dielectric constant for each compound, whereas the SMD model exhibits a significantly more variable free energy of solvation relationship with the solvent dielectric constant.

Comparative study on the gas to solution phase solvation free energies of model combustion flue gas compounds (N2, O2, CO2, H2O, SO2, and CO) in 178 organic solvents using the IEFPCM-UFF, CPCM, and SMD implicit solvent models at the Gaussian-4 (G4) level of theory

Gas to solution phase Gibbs free energies of solvation at 298.15 K for transfer of six representative combustion flue gas compounds (N~2~, O~2~, CO~2~, H~2~O, SO~2~, and CO) were calculated at the Gaussian-4 (G4) level of theory using the IEFPCM-UFF, CPCM, and SMD implicit solvent models for 178 organic solvents. The IEFPCM-UFF and CPCM models yield similar free energies of solvation for all six compounds in each of the solvents considered, having maximum absolute intra-solvent deviations <1.6 kJ mol^-1^. Substantial free energy of solvation differences were observed between the IEFPCM-UFF/CPCM and SMD models, with maximum absolute intra-solvent deviations up to 45.5 kJ mol^-1^. The IEFPCM-UFF and CPCM models displayed strong free energy of solvation correlations with the solvent dielectric constant for each compound, whereas the SMD model exhibits a significantly more variable free energy of solvation relationship with the solvent dielectric constant.

Morphology and photophysical properties of luminescent electrospun fibers prepared from diblock and triblock polyfluorene-block-Poly(2-vinylpyridine)/PEO blends

We successfully prepared luminescent electrospun (ES) fibers from the polymer blends of diblock poly[2,7-(9,9-dihexylfluorene)]-block-poly(2-vinylpyridine)(di-PFPVP) or triblock P2VP-b-PF-b-P2VP (tri-PFPVP) with polyethylene oxide (PEO) using a single-capillary spinneret. The morphology and photophysical properties of ES fibers were explored via the molecular architecture, solvent selectivity, and different molecular weights of PEO. The ES fibers had diameters around 400–800 nm using solvent of methanol (MeOH)/H2O while those using CHCl3 were around 1–3 μm, which was probably due to the difference on the solvent dielectric constant. Furthermore, the PF aggregated size and emission peak maximum in the ES fibers increased with enhancing the block copolymer composition using CHCl3. However, an insignificant variation was observed using MeOH/H2O. The larger PF aggregated size of the di-PFPVP/PEO blend ES fibers resulted in the red-shifting and broader emission peak, in comparison with that of the tri-PFPVP/PEO blend ES fibers. The efficient interaction of the PEO with the PVP block in two different block copolymers accounted for the above results. In the ES fibers using the low molecular weight of PEO (Mn~100 K), it exhibited a red-shifting on the PL spectra in comparison with the spin-coated films due to the geometrical confinement. Nevertheless, such confinement was probably significantly reduced using the high molecular weight PEO (Mn~2000 K) and thus an insignificant variation was found on the PL spectra. The present study demonstrated that their aggregate morphology and photophysical properties of ES fibers prepared from conjugated rod-coil block copolymer blends could be significantly tuned through polymer architecture, solvent selectivity, and copolymer composition.

Strong Micro-Dielectric Environment Effect on the Band Gaps of (n,m)Single-Walled Carbon Nanotubes

The electronic states of carbon nanotubes are one of the most fundamental properties of the nanotubes. We now describe the finding that the band gaps of (n,m)SWNTs are strongly affected by the change in microdielectric environments around the isolated nanotubes. In situ photoluminescence (PL) spectroelectrochemistry of the films containing 15 isolated (n,m)single-walled carbon nanotubes (SWNTs) cast on ITO electrodes in organic solvents including DMSO, acetonitirile, DMF, THF, and chloroform was completed and then the oxidation and reduction potentials, and band gaps (ΔE(electr)) of the (n,m)SWNTs in the solvents were determined. We have discovered that the ΔE(electr) of the (n,m)SWNTs become greater as the solvent dielectric constants decreased, which is in sharp contrast to the optical band gaps (ΔE(opt)) that show virtually no solvent dependence. Such a strong solvent dependence of the electrochemical band gaps is due to the difference in the solvation energy of the charged SWNTs produced during the electrochemical processes. The ΔE(electr) of both mod types of the SWNTs, mod = 1 and mod = 2, linearly increased versus the reciprocal of the tube diameter, which agrees with the theory. Moreover, the states of the π-electrons in the SWNTs were evaluated from the dependence of the band gaps on the diameter of the SWNTs. Furthermore, the states of the π-electrons on the sidewalls of the SWNTs were evaluated using the γ(0) values, a parameter representing the measure of the stability or the degree of delocalization of π-electrons in the sidewall of the SWNTs, and revealed that the γ(0) values of the mod = 1 and mod = 2 SWNTs increased with a decrease in the dielectric constants of the solvents in the range of 38-79. This study has enabled us to understand the essential electronic properties of the carbon nanotubes.

Changes induced by solvent polarity in electronic absorption spectra of some azo disperse dyes

The electronic absorption spectra of some azo disperse dyes in various solvents of different polarities have been studied at room temperature. The solvent effects on the wavenumbers of the absorption band maxima ( ṽ max) were discussed using the following solvent parameters, refractive index, n, dielectric constant, ε and empirical Kamlet–Taft solvent parameters, π* (dipolarity/polarizability), α (hydrogen bond donating capacity) and β (hydrogen bond accepting ability). The solute–solvent interactions were determined on the basis of multilinear solvation energy relationships concept. The fitting coefficients obtained from this analysis allowed us to estimate the contribution of each type of interactions to the total spectral shifts in solution. The established dependences between ṽ max and the solvent parameters emphasize that the visible band of the studied molecules is affected by both non-specific and specific solute–solvent interactions.

Competing effects of silanol surface concentration and solvent dielectric constant on electrostatic layer-by-layer assembly of silica nanoparticles on gold

Two types of silica nanoparticles having differing concentrations of ionizable surface groups are used to investigate the interplay between nanoparticle surface charge and solvent dielectric constant in nanostructure development during layer-by-layer assembly with a cationic polyacrylamide. Zeta ( ζ) potential measurements are used to determine the extent of silanol dissociation with pH. For 19-nm-diameter X-Tec 3408 silica nanoparticles from Nano-X GmbH (NanoX), complete dissociation yields a ζ-potential value of about −44 mV and occurs between pH 5 and 6 in 50% ethanol-in-water mixture by volume. By contrast, 65-nm-diameter polishing silica from Electron Microscopy Supply (EMS) has a ζ potential that does not equilibrate even up to pH 7 with a value of −59 mV under otherwise similar solution conditions. The more negative zeta potential at a given pH is found to substantially reduce nanoparticle adsorption. This behavior is opposite that observed when the dielectric constant of the suspension is decreased, independent of particle size. Nanoparticle surface chemical heterogeneity is discussed as a plausible explanation for such seriously discrepant behavior and the effects on multilayer electrical contact resistance for proton-exchange membrane (PEM) fuel-cell coating applications are presented.

Density functional study on chirospectra of hydrogen-bonded systems X− (H2O)3 (X = F, Cl, Br, I)

This paper calculates the molecular structures, infrared, Raman, circular dichroism spectra and optical rotatory powers of some hydrogen-bonded supramolecular systems as a cyclic water trimer, (H2O)3 and its pyramidal halide complexes, X− (H2O)3 (X = F, Cl, Br, I) with the gradient-corrected density functional theory method at the B3LYP/6–311++G(2d,2p) and B3LYP/Aug–cc–pVTZ levels. It finds that the complexation of halide anions with the water trimer can efficiently modulate the chirally optical behaviors. The calculated vibrational circular dichroism spectrum illuminates that the vibrational rotational strength of S(+)–(H2O)3 mostly originates from the O–H rocking modes, whereas chirality of S(–)–X− (H2O)3 (X = F, Cl, Br, I) has its important origin in the O–H stretching modes. The calculated optical rotatory power demonstrates that S(+)–(H2O)3 and S(+)–F−(H2O)3 are positively chiral, whereas S(–)–X−(H2O)3 (X = Cl, Br, I) are negatively chiral. With the polarizable continuum model, calculated bulk solvent effect in the solvents water and carbontetrachloride and argon shows that the positive chirality of S(+)–(H2O)3 is enhanced and the negative chirality of S(–)–X−(H2O)3 (X = Cl, Br, I) and the positive chirality of S(+)–F−(H2O)3 are reduced with an augmentation of the solvent dielectric constant.

Free Energies of Solvation with Surface, Volume, and Local Electrostatic Effects and Atomic Surface Tensions to Represent the First Solvation Shell.

Building on the SVPE (surface and volume polarization for electrostatics) model for electrostatic contributions to the free energy of solvation with explicit consideration of both surface and volume polarization effects, on the SMx approach to including first-solvation-shell contributions, and on the linear relationship between the electric field and short-range electrostatic contributions found by Chipman, we have developed a new method for computing absolute aqueous solvation free energies by combining the SVPE method with semiempirical terms that account for effects beyond bulk electrostatics. The new method is called SMVLE, and the elements it contains are denoted by SVPE-CDSL where SVPE denotes accounting for bulk electrostatic interactions between solute and solvent with both surface and volume contributions, CDS denotes the inclusion of solvent cavitation, changes in dispersion energy, and possible changes in local solvent structure by a semiempirical term utilizing geometry-dependent atomic surface tensions as implemented in SMx models, and L represents the local electrostatic effect derived from the outward-directed normal electric field on the cavity surface. The semiempirical CDS and L terms together represent the deviation of short-range contributions to the free energy of solvation from those accounted for by the SVPE term based on the bulk solvent dielectric constant. A solute training set containing a broad range of molecules used previously in the development of SM6 is used here for SMVLE model calibration. The aqueous solvation free energies predicted by the parameterized SMVLE model correlate exceedingly well with experimental values. The square of the correlation coefficient is 0.9949 and the slope is 1.0079. Comparison of the final SMVLE model against the earlier SMx solvation model shows that the parameterized SMVLE model not only yields good accuracy for neutrals but also significantly increases the accuracy for ions, making it the best implicit solvation model to date for aqueous solvation free energies of ions. The semiempirical terms associated with the outward-directed electric field account in a physical way for the improvement in the predictive accuracy for ions. The SMVLE method greatly decreases the need to include explicit water molecules for accurate modeling of solvation free energies of ions.

Fluorescence photoswitching of a diarylethene-perylenebisimide dyad based on intramolecular electron transfer

A fluorescent photochromic molecule, which is composed of a photochromic diarylethene (DE) and a fluorescent perylenebisimide (PBI), was synthesized and its fluorescence photoswitching was studied. The fluorescence quantum yield of the open-ring isomer is constant irrespective of solvent polarity, while that of the closed-ring isomer decreases with an increase in the dielectric constant of solvents. Femtosecond time-resolved transient and fluorescence lifetime measurements revealed that the fluorescence quenching of the closed-ring isomer is attributed to the intramolecular electron transfer from the PBI chromophore to the DE unit.

Kinetics and mechanism of acid catalyzed oxidation of phenol and substituted phenols by isoquinolinium bromochromate

Oxidation of phenols by isoquinolinium bromochromate (IQBC) in aqueous acetic acid leads to the formation of corresponding quinones. The reaction is first order with respect to both phenol and IQBC and catalysed by hydrogen ion. The rate of oxidation decreases with increase in dielectric constant of solvent indicating ion-dipole interaction. The rate of oxidation decreases with increase in concentration of KCl, this may be due to the formation of less reactive species by interaction of Cl− and protonated IQBC. The specific rates of oxidizing phenol reaction correlate with substituents constants affording negative reaction constants. Hammett plot is found to be valid and the correlation between enthalpies and free energies of activation is reasonably linear with an isokinetic temperature of 320 K.

Solvent Effect in the Reaction between Bis[1,2-di(trifluoromethyl) ethylene-1,2-dithiolato] Nickel and Butadiene

We studied the reaction mechanism for the reaction between bis[1,2-di(trifluoromethyl) ethylene-1,2-dithiolato] nickel (Ni[S(2)C(2)(CF(3))(2)](2)) and butadiene by density functional theory (DFT) at the B3LYP/6-31G(d) level. The solvent effect on the charge distribution, dipole moment, and solvation free energies of the stationary points were investigated using the polarizable continuum model (PCM). The calculation results showed that this reaction was orbital symmetry allowed and concerted. The reaction stationary points become more stable with an increase of solvent dielectric constant. Additionally, the degree of stabilization for the transition state and the product is larger than that of the reactants in the same solvent, which means that the reaction occurs more easily.