Determination of three-dimensional solubility parameters of styrene butadiene rubber and the potential application in tire tread formula design

Equilibrium swelling measurement was employed to correlate the Hildebrand (one-dimensional) solubility parameter (δ) of styrene butadiene rubber (SBR) with using different kinds of solvents. The δ was estimated to be a range from 17 MPa^1/2 to 19 MPa^1/2. It was attempted to calculate the three-dimensional solubility parameter (HSP) of SBR by inputting the swelling data into a professional software program, and the output results were δ_d = 18.0 MPa^1/2, δ_p = 2.9 MPa^1/2 and δ_H = 2.3 MPa^1/2. A new Flory-Huggins interaction parameter (χ_HSP) between SBR and solvents was calculated by HSP values for the purpose of better predicting rubber swelling responses. The results turned out that the swelling ratio (q) increased with a decrease of χ_HSP value, showing a roughly linear relationship. Furthermore, a correlation index relating to χ_HSP value was introduced and mathematical fitted as a functional equation in this work. By using this equation, it is easy to characterize the relative interactions between SBR and each ingredient involved in the formulation and make a pre-screening of the candidate additives for the formula design. Taking advantage of this method one can response better to the challenges in selecting the most suitable additives and replacing the outdated ones by the new emerging ones, bio-sourcing with environmentally friendly ones in particular.     

A new way to determine the three-dimensional solubility parameters of hydrogenated nitrile rubber and the predictive power

In order to understand the swelling behavior of hydrogenated nitrile rubber (HNBR) more fully, the total solubility parameters (δ_t) of HNBR (Therban 2568) were determined by equilibrium swelling tests. Then, the swelling responses were analysed by a computer program to determine the Hansen three-dimensional solubility parameter (HSP). The HSP values – determined from lightly cured rubber samples – were estimated as δ_d = 18.4 (J/cm³)^1/2, δ_p = 6.0 (J/cm³)^1/2, δ_h = 4.5 (J/cm³)^1/2 and δ_t = 19.9 (J/cm³)^1/2. The energy difference (Ra) between HNBR and solvents or solvent mixtures have been calculated by their HSP values and proven to be useful for predicting the swelling behaviour of HNBR. The swelling volume decreases with increasing Ra values. Using blended solvents, a clear correlation between Ra values and the rubber swelling response was established. Thus, it may be possible to use the Hansen three-dimensional solubility parameters to predict swelling phenomena of cured rubber articles in mixed fluids such as bio-fuels or lubricants. Also, the HSP values may be used to predict the response of rubber seals or gaskets when replacing toxic or expensive fluids with more favorable environmentally friendly or inexpensive ones.     

14/15N-NMR und 11B-NMR-Daten von Trifluormethylthioaminoboranen mit natürlicher Isotopenhäufigkeit

^14/15N N.M.R. and ¹¹B N.M.R. Data of Trifluoromethylthioamino-boranes with Natural Isotope Abundance (Part 2) ^14/15N as well as ¹¹B-NMR data for trifluoromethylthioabminoboranes of the types XnB[N(SCF₃)₂], with X = F, Cl, Br, N₃, or NHSCF₃, n = 0, 1 or 2, and Cl_3?nB(NHSCF₃)n with n = 1, 2 or 3, as well as for the amine-borne Me₃NBCl₂N(SCF₃)₂ and the cyclic borazene (CF₃SNHBNH)₃ are reported. These data are used, together with a qualitative analysis of the bonding situation based on observed rotational barriers and known structures, to analyse for B ← N back donation in these compounds. Relatively small variations in δ^14/15N compared to those observed for alkylaminoboranes as well as large variations in δ¹¹B are suggestive of small contributions only from back bonding. In addition the ?halogene like”? nature of the (CF₃S)₂N group is confirmed. For the series X₂BN(SCF₃)₂ (X = F, Cl, Br on N₃), XB[N(SCF₃)₂]₂ (X = Cl, Br, N₃ or N(SCF₃)₂) and Cl_n?3B(NHSCF₃)_n (n = 1, 2 or 3) a linear relationship for δ¹¹B and δ^14/15N is observed. It is furtheron demonstrated that hitherto known δ^14/15N/¹¹B correlations are valid only in case of strong B ← N back donation.     

The thermodynamics of dissolution of low-molecular-mass compounds in polymethyl[2′-(3-trifluoromethyl-2,2,3-trifluorocyclobutyl)ethyl]siloxane studied via inverse gas chromatography

The effect of the 2′-(3-trifluoromethyl-2,2,3-trifluorocyclobutyl)ethyl radical in fluorosiloxane on the thermodynamics of dissolution of various low-molecular-mass compounds in this polymer is studied via inverse gas chromatography. The activity coefficients at infinite dilution, Ω ₁ ^∞ , in the temperature range 20–100°C are determined for C₆–C₈ n-alkanes, cyclohexane, benzene, toluene, tetrachloromethane, trichloromethane, 2-butanone, and ethyl acetate. Flory-Huggins interaction parameters χ ₁₂ ^∞ are calculated. It is shown that hydrocarbons are poor solvents (Ω ₁ ^∞ > 6, χ ₁₂ ^∞ > 0.5) and that the studied fluorosiloxane is not inferior to commercial polymethyl(3,3,3-trifluoropropyl)siloxane with respect to stability in nonpolar liquid media in the range 20–70°C. Trichloromethane (above 50°C) and compounds containing a carbonyl group are found to be good solvents. The dispersion component of the solubility of the polymer, δ ₂, is determined to be 14.0 (J/cm³)^1/2 at 20°C and slightly lower, 13.5 (J/cm³)^1/2, at 100°C. Possible causes of these low values of δ₂ are discussed.     

Surface Tension and the Solubility of Polymers and Biopolymers: The Role of Polar and Apolar Interfacial Free Energies

Surface tension data can be used for estimating the solubility of polymers in liquids. By determining the apolar and the polar components of the surface tension of polymers and of solvents, the attractive free energy, δG ₁₂₁, of a polymer (1) in a given solvent (2) can be established. By also taking into account the contactable surface area of two polymer molecules, immersed in a liquid, δG ₁₂₁ can be expressed in units of kT. Solubility then is favored when -1.5 kT < δG ₁₂₁ < 0 for apolar systems, and when -1.5 kT < δG ₁₂₁ for polar systems. In polar solvents, hydrogen bonding can often increase δG ₁₂₁ from <-1.5 kT to > + 1.5 kT. Positive values are frequently attained and this strongly shifts the behavior from insolubility to solubility. A number of proteins exemplify this behavior.     

Solvent effects on the geometry,electronic structure,and bonding style of Zn(N5)2: A theoretical study

Nitrogen-rich compounds involving the cyclo-pentazole anion (cyclo-N₅⁻) have attracted extensive attention due to higher energy release and environmental friendliness than traditional high energy density materials (HEDMs). However, the synthesis of stable HEDMs with cyclo-N₅⁻ is still a challenge. In this study, the effect of nine solvents on the geometrical and electronic structures and solvation energies of Zn(N₅)₂, one of the recently synthesized nitrogen-rich compounds, was studied using the density functional theory and the polarized continuum model. The results indicated an increase in the stability of Zn(N₅)₂ in the solution phase compared to the vacuum phase, and the stability of Zn(N₅)₂ increases with increasing dielectric constants. The energy gap of frontier molecular orbitals and the absolute value of total energy in water are the largest, revealing that Zn(N₅)₂ is more stable in water than in other solvents. To understand the stabilization mechanism of Zn(N₅)₂ by water, further studies were performed with the natural bond orbital (NBO) analysis and the quantum theory of atoms in molecules (QTAIM) analysis using the explicit solvent model. The charge transfer and the hydrogen bonds are observed between Zn(N₅)₂ and water, which are beneficial to improvement of the stability of Zn(N₅)₂. This may indicate the solvents that have strong interactions with the cyclo-N₅⁻ candidate may improve the possibility of success of synthesis.     

Effect of alkaline and alkaline–earth cations on the supercapacitor performance of MnO2 with various crystallographic structures

The electrochemical performances of the α-, γ-, and δ-MnO₂ with different crystallographic structures were systematically investigated in 0.5 mol/L Li₂SO₄, 0.5 mol/L Na₂SO₄, 1 mol/L Ca(NO₃)₂, and 1 mol/L?Mg(NO₃)₂ electrolytes. The results showed that the electrochemical performances of the manganese dioxides depended strongly on the crystallographic structures of MnO₂ as well as the cation in the electrolytes. Because the δ-MnO₂ consists with layers of structure and the interlayer separation is 7 Å, which is suitable for insertion/extraction of some alkaline and alkaline–earth cations, the δ-MnO₂ electrode showed the higher specific capacitance than that of α-MnO₂ and γ-MnO₂. We also found that the α-, γ-, and δ-MnO₂ electrodes in the Mg(NO₃)₂ electrolyte showed a higher specific capacitance, while all the α-, γ-, and δ-MnO₂ electrodes in the Li₂SO₄ electrolyte exhibited a better cycle life. The reason for the different behavior of Li⁺ and Mg²⁺ during the charge/discharge process can be ascribed to the charge effect of the cations in the electrolytes. The ex situ X-ray diffraction (XRD) and long-time cyclic voltammogram measurements were used to systematically study the energy storage mechanism of MnO₂-based electrodes. A progressive crystallinity loss of the materials is also observed upon potential cycling at the oxidized states. A reasonable charge/discharge mechanism is proposed in this work.     

Darstellung und spektroskopische Charakterisierung der reinen Bindungsisomeren [OsCl5(NCS)]2− und [OsCl5(SCN)]2−

Preparation and Spectroscopic Characterization of the Pure Bondisomers [OsCl₅(NCS)]^2? and [OsCl₅(SCN)]^2? The oxidation of [OsCl₅I]^2? with (SCN)₂ in CH₂Cl₂ yields the bondisomers [OsCl₅(NCS)]^2? and [OsCl₅(SCN)]^2?, which are isolated as pure compounds by ion exchange chromatography on DEAE-Cellulose. Only the salts of the N-isomer show significant shifts in the vibrational and electronic spectra caused by polarization of the terminal S depending on the size of the cations and the polarity of the solvents. In the IR and Raman spectra ν_CN(S), ν_CS(N) and δ_NCS are found at higher wave numbers than ν_CN(N), ν_CS(S) and δ_SCN. In the optical spectrum of the red [OsCl₅(SCN)]^2? the charge-transfer S→Os is nearly constant at 538 nm, but the N→Os transition of the yellow to violet coloured N-isomer shifts from 480 nm in organic solvents or in presence of large alkylammonium cations to 516 nm in aqueous solution and to 544 nm in the solid Cs-salt. The optical electronegativities are calculated to χ_opt(–SCN) = 2.6 and χ_opt(–NCS) = 2.6–2.8. According to spinorbit coupling and to lowered symmetry (C_4v) the splitted intraconfigurational transitions are observed at 10 K as weak peaks in the regions 600, 1000 and 2000 nm. The O? O transitions are calculated from the vibrational fine structure. The lowest level of both isomers is confirmed by peaks in the electronic raman spectra. With the parameters ζ(Os^IV) = 3200 cm^?1 and B(? SCN) = 316 cm^?1 or B(? NCS) = 288 cm^?1 there is a good fit of calculated and experimental data, resulting in the nephelauxetic series: F^? > CI^? > SCN^? > Br^? > NCS^? > I^?.     

Zur Interpretation 29Si-NMR-chemischer Verschiebungen

The ²⁹Si-NMR chemical shifts δ(²⁹Si) of (CH₃)_4?nSiX_n compounds and some ¹³C-NMR chemical shifts δ(¹³C) of analogous carbon compounds are discussed by means of relative paramagnetic screening constants σ*, calculated by a simplified model. In this model only the Si(3P)- and C(2P)-orbitals are considered; for the calculations, the electronegativities of Si, C and the X-substituents and a single empirical parameter are necessary. The calculated values of σ* are in good agreement with the change of the chemical shifts which are observed for the (CH₃)_4?nMX_n compounds with different X and n. These results clearly show that δ(²⁹Si) and δ(¹³C) depend primarily on the σ-charge of the Si- and C-atom, and that (P? d)π-interactions on the Si-atom are of minor importance.     

15N-, 1H-, and 13C-NMR chemical shifts and electronic properties of aromatic diamines and dianhydrides

We measured the ¹⁵N-, ¹H-, and ¹³C-NMR chemical shifts for a series of aromatic diamines and aromatic tetracarboxylic dianhydrides dissolved in DMSO-d₆, and discuss the relationships between these chemical shifts and the rate constants of acylation (k) as well as such electronic-property-related parameters such as ionization potential (IP), electronic affinity (EA), and the energy ε of the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO). The ¹⁵N chemical shifts of the amino group of diamines (δ_N) depend monotonically on the logarithm of k (log k) and on IP. We inferred the reactivities of diamines whose acylation rates have not been measured from their δ_N, and we propose an arrangement of diamines in the order of their reactivity. The ¹H chemical shift of amino hydrogens (δ_H) and the ¹³C chemical shift of carbons bonded to nitrogen (δ_C) are roughly proportional to δ_N, but these shifts are not as closely correlated with log k and IP. Although the ¹³C chemical shifts of the carbonyl carbon of dianhydrides (δ_C,) varies much less than the δ_C and δ_N of diamines, δ_C, can be an index of acylation reactivity for dianhydrides because it is closely correlated with ε_LUMO. These facts indicate that the chemical shifts of diamines and dianhydrides are displaced according to their electron-donor and electron-acceptor properties, and that these chemical shifts can be used as indices of the electronic properties of monomers. Changes in reactivity caused by the introduction of trifluoromethyl groups into diamines and dianhydrides are inferred from the displacements of δ_N and δ_C © 1992 John Wiley & Sons, Inc.     

Photophysical Behavior of Angelicins and Thioangelicins: Semiempirical Calculations and Experimental Study

The decay processes of the lowest excited singlet and triplet states of five methylated angelicins (4,6,4′-trimethyl-angelicin, MA, and four methylated thioangelicins, MTA; see Scheme 1) were investigated in live solvents by stationary and pulsed fluorometric and flash photolytic techniques. In particular, the solvent effects on absorption, fluorescence, quantum yields of fluorescence (φ_F) and triplet formation (φ_T), lifetimes of fluorescence (τ_F) and the triplet state (τ_T) and the quantum yields of singlet oxygen production (φ_Δ) were investigated. Semiempirical (ZINDO/S-CI) calculations were carried out to obtain information (transition probabilities and nature) on the lowest excited singlet and triplet states. The quantum mechanical calculations and the solvent effect on the photophysical properties showed that the lowest excited singlet state (S¹) is a partially allowed π,π* state, while the close-lying S₂ state is n,π* in nature. The efficiencies of fluorescence, S₁→T₁ intersystem crossing (ISC) and S₁→ S₀ internal conversion (IC) strongly depend on the energy gap between S₁, and S₂ and are explained in terms of the so-called proximity effect. In fact, for MA in cyclohexane, only the S₁→ S₀ internal conversion is operative, while in acetonitrile and ethanol, where the n.π* state is shifted to higher energy, the efficiencies of fluorescence and ISC increase significantly. The energy gap between S₁ and S₂ increases in MTA, where the furanic oxygen is replaced by a sulfur atom. Consequently, the solvent effect on the photophysical parameters of MTA is less marked than for MA; e.g. fluorescence and triplet-triplet absorption are also detectable in the nonpolar cyclohexane. The lowest excited singlet state of molecular oxygen O₂(¹D_g) was produced efficiently in polar solvents by energy transfer from the T₁ state of MA and MTA.     

Darstellung und Charakterisierung von Bindungsisomeren Bromorhodanorhenaten(IV)

Preparation and characterization of bondisomeric bromorhodanorhenates(IV) The new compounds [ReBr₅(SCN)]^2?, [ReBr₅(NCS)]^2?, cis/tr.-[ReBr₄(NCS)(SCN)]^2?, cis-[ReBr₄(NCS)₂]^2?, mer-[ReBr₃(NCS)₃]^2? are prepared from [ReBr₆]^2? by ligand exchange with NaSCN, KSCN, or (SCN)₂ in organic solvents and isolated by ion exchange chromatography on DEAE cellulose. The bondisomers are significantly distinguished by the frequencies of inner ligand vibrations: v_CN(S) > v_CN(N), v_CS(N) > v_CS(S), δ_NCS δ_SCN. The electronic absorption spectra measured at 10 K exhibit in the region 5700 to 15300 cm^?1 all intraconfigurational transitions (t_2g³) splitted into 8 Kramers doublets by lowered symmetry (C_4v, C_2v, C_s) and spin orbit coupling. The O–O-transitions are deduced form vibrational fine structure and confirmed by electronic Raman bands in some cases. The magnetic moments are in the range of 3.0 to 3.9 B.M.     

New insights into Hansen's solubility parameters

Correlations among the three components, δ_d² (dispersion), δ_h² (hydrogen‐bonding), and δ_p² (polar) that make up the Hansen solubility parameter equation, δ_o² = δ_d² + δ_h² + δ_p², have been analyzed for a large number of organic solvents. A relationship is found that enables δ_h and δ_p to be estimated if δ_o and δ_d are known. This relationship is applied to a variety of common polymers and remarkably good agreement is obtained with tabulated values for δ_h and δ_p. Additional correlations are found that can be expressed in approximate functional form. The analysis also reveals relationships, expressed as inequalities, among the parameters that limit their range of possible values. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 4337–4343, 2004     

Computational study of osmabenzyne: The solvent effects on the structure and spectroscopic properties (IR,NMR)

In this article, the structural, electronic, and spectroscopic properties of osmabenzyne Os{≡CC(SiH₃)=C(CH₃)C(SiH₃)=CH}Cl₂(PH₃)₂ are explored in the gas phase and five solvents. The effects of solvents on the structural parameters, frontier orbital energies, and spectroscopic parameters of the complex are elucidated using the polarizable continuum model. The wavenumbers of selected IR-active vibrations in different solvents are obtained and correlated with the Kirkwood–Bauer–Magat equation. In addition, thermodynamic parameters of solvation are calculated for the complex. ¹H and ¹³C NMR chemical shifts are estimated using the gauge-invariant atomic orbital method.     

Solubility parameters of poly(sulfonyldiphenylene phenylphosphonate) and its miscibility with poly(ethylene terephthalate)

The solubility behaviors of poly(sulfonyldiphenylene phenylphosphonate) (PSPPP), a very efficient flame retardant for poly(ethylene terephthalate) (PET), in more than 50 solvents were examined. Its solubility parameters (δ) were determined by the intrinsic viscosity and turbidic titration methods. The two methods obtained consistent results, δ = 21.0–21.6 J^1/2/cm^3/2 and δ = 21.0 J^1/2/cm^3/2, and the three‐dimensional solubility parameters were δ_d = 18.9 J^1/2/cm^3/2, δ_p = 8.8 J^1/2/cm^3/2, and δ_h = 5.9 J^1/2/cm^3/2. The miscibility of PSPPP with PET was estimated by the calculation of the heats of mixing, which were related to the difference between the solubility parameters of PSPPP and PET. Fourier transform infrared was used to examine the interactions between PSPPP and PET macromolecules, which were the internal factors of polymer–polymer miscibility. The results showed that PSPPP and PET were miscible within a very wide composition range, especially with less than 15 wt % PSPPP, a composition of interest for the preparation of flame‐retardant PET. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2296–2301, 2003     

Solubility and Solution Thermodynamics of Some Sulfonamides in 1-Propanol + Water Mixtures

The solubilities of sulfadiazine (SD), sulfamerazine (SMR) and sulfamethazine (SMT) in some 1-propanol + water co-solvent mixtures were measured at five temperatures from 293.15 to 313.15 K over the polarity range provided by the aqueous solvent mixtures. The mole fraction solubility of all these sulfonamides was maximal in the 0.80 mass fraction of 1-propanol solvent mixture (δ _solv = 28.3 MPa^1/2) and minimal in water (δ = 47.8 MPa^1/2) at all temperatures studied. The apparent thermodynamic functions Gibbs energy, enthalpy, and entropy of solution were obtained from these solubility data by using the van’t Hoff and Gibbs equations. Apparent thermodynamic quantities of mixing were also calculated by using the ideal solubilities reported in the literature. Nonlinear enthalpy–entropy relationships were observed for these drugs in the plots of enthalpy versus Gibbs energy of mixing. The plot of ?_mix H° versus ?_mix G° shows different trends according to the slopes obtained when the mixture compositions change. Accordingly, the mechanism for the solution process of SD and SMT in water-rich mixtures is enthalpy driven, whereas it is entropy driven for SMR. In a different way, in 1-propanol-rich mixtures the mechanism is enthalpy driven for SD and SMR and entropy driven for SMT. Ultimately, in almost all of the intermediate compositions, the mechanism is enthalpy driven. Nevertheless, the molecular events involved in the solution processes remain unclear.     

The conformational energy difference for δ-valerolactone

The temperatuure dependence of the vicinal OCH₂CH₂ coupling constant in the six-membered ring δ-valerolactone suggests the presence of at least two conformers of unequal energy. Analysis of this temperature dependence by the Wood-Fickett-Kirkwood method in six solvents produces free energy differences in the narrow range 0.8–1.4 kcal mol^?1, with a mean of 1.0 kcal mol^?1 and no apparent dependence on solvent polarity. Thus the two conformers, probably the half-chair and the classic boat, have similar polarities. The analogous four- and five-membered lactones show little or no temperature dependence for their analogous coupling constants, in agreement with the presence of a single conformation for these rings.     

Linear free energy relationships for carbon-13 NMR chemical shifts of substituted benzoic acids1

In order to examine ¹³C-SCS of substituted benzoic acids, chemical shifts of the acid form (I) and the dissociated form (II) have been obtained separately. Single substituent parameters, σ⁰ or σ⁺ are correlated with the shifts for the carboxyl (δ_co) or ipso carbons (δ_ipso), respectively. Among the available five equations which are developed for the analysis with dual (or divided) substituent parameters (DSP), the Swain-Lupton equation (eqn 3) and the Taft-Swain-Lupton equation (eqn 4) give much better correlations, not only for δ_co and δ_ipso but also for the results for ring carbons (C(2), C(5), C(6)), except for those attached to or neighboured by substituents. It is concluded that the SCS of aromatic compounds are best analyzed with substituent parameters derived from reactions or equilibria on the basis of linear free energy relationships.