Theoretical analysis of sorption of a binary solvent in a polymer phase. I. Occurrence and character of inversion in preferential sorption

Osmotic and sorption equilibria in the system polymer–binary solvent can be represented with advantage in coordinates (u₁, v₃), where v₃ is the volume fraction of the polymer and u₁ gives the composition (volume fraction) of the binary solvent in the polymer phase. The coexistence lines and osmotic isobars are plotted; the former are used to read the preferential sorption ε of one of the solvent components in the polymer. The newly formulated equilibrium condition for the preferential sorption is applied to the Flory–Huggins theory extended by the ternary interaction parameter χ_T. This is used as a starting point for analyzing the conditions under which inversion of preferential sorption takes place, i.e., the sign of ε changes. The existence of inversion and the course of the inversion line in the v₃ versus u₁ plot are affected in a decisive manner by the extent to which the effect of the mutual interaction of solvent components prevails over the effect of the relative difference between their molar volumes and of the difference in strength of their interaction with the polymer. The effect of the ratio of molar volumes upon the preferential sorption increases with the concentration of the polymer, so that for v₃ not too far from unity the component having the smaller molecule is necessarily sorbed preferentially. If, therefore, both types of small molecules are not of the same size, the inversion vanishes for large v₃ even in systems where it actually occurs if v₃ is small. On the contrary, the same effect can in other cases have as its consequence an inversion at moderate values of v₃, even if it does not appear as v₃ approaches zero; a similar effect can also be produced by a nonzero value of the interaction parameter χ_T. The neighborhood of the inversion line can have a “divergent” or a “convergent” character, depending on whether the component being preferentially sorbed is that present in excess. The former case is observed with negative and the latter for the positive values of the binary solvent–solvent interaction parameter χ₁₂. The inversion with the divergent neighborhood has not yet been confirmed experimentally, owing to the small number of systems investigated.     

Conformational properties of polar polymers. I. Poly(vinyl chloride)

A recently developed method for including polar bonds in conformational energy calculations is applied to poly(vinyl chloride). Inductive effects on dipole moments and the effects of intervening atoms on electrostatic interaction energies are represented by polarizability centers in conjunction with bond centered dipoles. Solvation energies are estimated by means of a continuum dipole–quadrupole electrostatic model. Calculated energies of a number of conformations of meso and racemic 2,4-dichloropentane and the iso, syndio, and hetero forms of 2,4,6-trichloroheptane give satisfactory representations of isomer and conformer populations. Electrostatic effects are found to be quite important. However they appear to be effectively of sufficiently short range that the calculated conformer energies are found to be fit well by a linear combination of interaction parameters (consisting of gauche, skew chlorine, four-bond CH₂…CH₂, CH₂…Cl, and Cl…Cl interactions) conventional to vinyl polymers and a special four-bond interaction that arises when the bond sequence Cl? CH? CH²? CH? Cl is (nearly) coplanar. These interaction parameters when assembled into statistical weight matrices lead to calculated values of both the characteristic ratio and the dipole moment ratio in satisfactory agreement with experiment. Least energy paths for transitions between the most stable conformations are also calculated.     

Nature of the interaction between ammonia derivatives and carbon disulfide. A theoretical investigation

The interactions between NH₃, its methylated and chlorinated derivatives and CS₂ are investigated by ab initio CCSD(T) and density functional BLYP‐D3 methods. The CCSD(T)/aug‐cc‐pVTZ calculated interaction energies of complexes characterized by the S···N chalcogen bonds range between ?1.71 and ?2.78 kcal mol^?1. The S···N bonds are studied by atoms in molecules, natural bond orbital, and noncovalent interaction methods. The lack of correlation between the interaction energies of methylated amines complexes and the electrostatic potential results from the lone pair effect in aliphatic amines. Different structures of CS₂ complexed with ammonia derivatives, stabilized by other than the S···N chalcogen bonds, are also predicted. These structures are characterized by interaction energies ranging between 1.15 and 3.46 kcal mol^?1. The results show that the complexing ability of CS₂ is not very high but this molecule is able to attack the electrophilic or nucleophilic sites of a guest molecule.     

Study of singlet—triplet coupling in glyoxal by level anticrossing spectroscopy. V. Nature of singlet—triplet interaction

We observe in glyoxal cooled in a supersonic free jet the fluorescence of individual rotational levels of the S₁ state excited by a cw laser. We use the technique of singlet—triplet magnetic resonance near an anticrossing to measure matrix elements V₃₁ as a function of rotational quantum numbers N_s, N_t, K_s, K_t. The experimental results are compared with theoretical models of singlet—triplet couplings and we show that the spin-vibronic interaction is the dominant singlet—triplet interaction in glyoxal.     

Anionic polymerization of lactones initiated by alkali graphitides. II. Changes in the KC24 structure during polymerization of lactones

The structural changes in the potassium graphitide KC₂₄ in its interaction with ?-caprolactone, γ-butyrolactone and pivalolactone are examined by profilometric measurement and electron scanning microscopy. The interaction of KC₂₄ with a nonpolymerizable lactone-γ-butyrolactone proceeds without delamination of the graphitide. The polymerization of ?-caprolactone and pivalactone in the interlayer spaces of KC₂₄ leads to destruction of the initiators structure. An increase in the temperature and monomer concentration enhances the delamination of the graphitide.     

2H-N.M.R. studies of flexibility and orientational order in nematic liquid crystals

Abstract

Deuteron magnetic resonance spectroscopy (²H-N.M.R.) has been used to investigate the effect of the nematic environment on the flexibility and orientational order of two perdeuteriated cyanobiphenyl homologues: 4-methyl-4′-cyanobiphenyl (1CB-d ₁₁) and 4-n-pentyl-4′-cyanobiphenyl (5CB-d ₁₉). The systems studied were low concentrations of 1CB-d ₁₁ and 5CB-d ₁₉ dissolved in the nematic phases of 5CB, N-(-4-ethoxybenzylidene)-4′-n-butylaniline (EBBA), Merck ZLI-1132 (1132) and a 55wt% mixture of 1132: EBBA. The spectra are dramatically different in these environments. Previous studies on small solutes have suggested that in the 55wt% 1132: EBBA mixture (at 301.4 K) the dominant orienting mechanism depends on the size and shape of the molecule which suggests that it is a short range repulsive interaction. This interaction has been modelled by treating the liquid crystal as an elastic continuum and the solute as a collection of van der Waals spheres which stretch the liquid crystal in the two dimensions perpendicular to the director. The distortion of the liquid crystal depends on the dimensions of the solute, and the elastic energy is described in terms of a Hooke's law force constant, k. The model is extended to include flexible liquid crystal molecules and quadrupolar couplings are calculated for each conformation of the 5CB chain. Statistical averaging over all conformations gives an excellent fit to the experimental spectrum. The results for 1CB and 5CB show that in the other nematic phases contributions from additional mechanisms must be included. Previous studies of ²H₂ and other solutes indicate that the additional mechanism is the interaction between the solute molecular quadrupole moment and the mean electric field gradient of the liquid crystal.     

Molecular relaxation processes in triatomic molecules. II. The N2–CO2 system

Translation–vibration (T–V) and vibration–vibration (V–V) energy transfer processes in the N₂–CO₂ system were investigated using classical trajectory techniques. Two empirical interaction potentials were employed. One is comprised of independent, atom–atom Morse-type functions operating between nonbonded atoms. The other included these atom–atom Morse functions plus Coulombic terms to account for the quadrupole–quadrupole intertion. Both interaction potentials led to similar T–V results. However, the result that CO₂(v₃) is excited ～10³ times more efficiently than N₂(v = 1) was obtained, which is at variance with existing analytical theories of T–V energy transfer employing purely repulsive short-range potentials. Different V–V energy transfer probabilities were obtained from the two interaction potentials. The most important finding is that only when electrostatic orientation effects are combined with short-range repulsive interactions is the near-resonant V–V transfer found to be the dominant energy transfer path. This interaction potential also crudely accounts for the negative temperature dependence observed for this near-resonant V–V transfer at low temperatures (300–1000°K).     

Line shapes in electronic absorption spectra. Phenanthrene

The 3000 Å, (¹B₂ ← ¹A₁), absorption system of phenanthrene in durene crystals at 4°K illustrates an electronic transition, which is subject to near-resonance vibronic perturbations whose effect is intermediate to both the small (sparse intermediate) and large molecule (statistical) limits. Both broad (300 cm^?1) and narrow (10 cm^?1) lines are evident. A model is proposed which incorporates both these features by fast allowing for a consideration of the interaction between a small number of discrete levels, those associated with the largest coupling, followed by a treatment of the broadening of these levels through interaction with the remaining near continuum of states of the lower electronic state. Thus, one and the same electronic state provides both a sparse and dense manifold of levels. An important result of the model is that in terms of absorption intensities all the lines emerge with the same heights but differ in widths. When the intensities are summed with respect to energies this aspect is obscured. This approach has been shown to satisfactorily reproduce many of the features of the ¹B₂ absorption spectra of phenanthrene and phenanthrene-d₁₀. The ¹B₂ absorption systems have also been measured in the vapour phase and fine structure attributable to vibronic coupling and sequence band development are discussed.     

Neue Beobachtungen zum chemischen Transport von GeO2. III. Transportraten mit dem Transportmittel Wasserstoff

Novel Observations on the Chemical Transport of GeO₂. III. Rates of Transport with Hydrogen In the course of a chemical transport in the system GeO₂/H₂ the composition of the solid phases can change until a steady state is reached. In this case an iterative calculation of the equilibrium is now possible. The method takes into acount the mutual interaction of the processes in the source and in the zone of deposition and allows a general application. The participation of H₂ implies a large difference in the coefficients of diffusion which demands the estimation of the interaction of diffusion and laminar flow. The comparision of experimentally determined rates of transport with calculated values shows now that the increasing laminar flow is antagonistic to the deposition of GeO₂.     

Polymer brush in mixed solvent. The role of flory interaction parameter χAB of the solvent components

The properties of polymer brush in binary solvent are considered on the base of the mean-field theory. The role of the interaction parameter χ_AB of the two components on the brush parameters was specially considered. The mixture of two precipitants was shown to be a good solvent for the polymer brush provided that their interaction parameter χ_AB is sufficiently great.     

Structure investigations by P.A.C.

The perturbed angular correlation /P.A.C./ technique is employed to investigate the structures of barium ferrite and barium hexaferrite using radioactive¹³³Ba /10.7 Y/ as a probe. The quadrupole interaction frequencies /W_Q'S/ are found to be 9.68 and 12.02 Mrad sec^–1 for barium ferrite and barium hexaferrite, respectively, showing a drift from usual cubic structure.     

Polymer effect on electron-donating character of polymeric donor. I. Formation of charge-transfer complex between polymers containing N,N-dimethylaniline group and maleic anhydride

The difference in electron-donating character between polymeric and monomeric donors in their charge-transfer-complex formation reactions was studied to clarify the so-called polymer effect in such reactions. Systems containing maleic anhydride and copolymers of N,N-dimethyl-p-aminostyrene (ASt) with styrene, which were prepared by a conventional free-radical polymerization technique, were found to be suitable for this purpose. In correlations between the mean sequence length μ_ASt of the ASt units in the copolymers and the lowest energy of their charge-transfer transition (λ_max) or the association constant of their complex formation K_CT, a bathochromic shift in λ_max and an increase in K_CT with increasing μ_ASt of copolymers are found. Moreover, there is a difference in their modes of μ_ASt dependence. It was concluded from these results that the electron-donating character of the dimethylaniline group increases with increasing number of groups attached on one polymer chain. Also, there is an interaction among neighboring functional groups on one polymer chain. The interaction may be regarded as a kind of polymer effect. In addition, the difference in μ_ASt dependence between λ_max and K_CT and also thermodynamics of the complex formation are discussed.     

Role of CA2+ ion in the abortifacient action of prostaglandins. II. Molecular orbital and conformation energy calculations of PGA1

This paper reports some theoretical studies of PGA₁ using conformational and molecular orbital techniques. The conformation energy (CE ) calculations, using empirical potential-energy functions, for intrinsic torsional rotations around C₁₂? C₁₃ (θ), C₇? C₈ (Ψ), and C₁₄? C₁₅ (?) show a number of energy minima. The relative value of the CE for these minima ranges from 4.09 to 8.01 kcal/mol. An additional rotation around C₄? C₅ (χ) giving “twist” to the carboxyl chains lowers the CE value by 2–3 kcal/mol and a conformation with CE value 2.39 kcal/mol less than crystallographic one is obtained. The interchain interaction energy showed changes with conformations. No significant change in the interchain interaction energy was observed due to “twist” in the carboxyl chain. The isopotential mapping study demonstrated the probable ionic binding site near the carboxyl and the ring (O₉) oxygens. Conformational and molecular orbital results are discussed in the light of the reduced abortifacient potency of PGA₁ with respect to PGF_2α and the possible role of Ca²⁺ ions in this action.     

A simple reliable approximation for isotropic intermolecular forces. A critical test using HH(3Σu+) as a model

A simple semi-empirical approximation for the exchange energy (E_x), coupled with a tractable representation of the Coulomb energy (E_C), has been found to yield very accurate results for the isotropic part of the interaction energy (E_int = E_x + E_C) between two closed shell systems. The expression for E_int is based on the knowledge of the first order Coulomb energy and the first three terms in the asymptotic long range expansion of the second order Coulomb energy for the interaction and contains but one adjustable parameter which occurs in E_x. The usefulness of this approach for evaluating E_int is tested critically by using the non-bonded H(1s)H(1s) (³Σ_u⁺) interaction as a model (accurate values of the total interaction energy, the exchange energy, and various orders of Coulomb energies, are available for a wide range of R for this system). The results obtained for both E_int and (dE_int/dR) are inremarkable agreement with the exact results of Kotos and Wolniewicz for R > 3 a_o. Since the law of corresponding states for inert gas pairs holds equally well for the HH(³Σ_u⁺) interaction, our analysis of this simple system yields valuable information on the reliability of the approach for other van der Waals dimers.     

Viscosity of ternary mixtures. II. Water-tert-butyl alcohol-alkali halides

The viscosities of binary alkali halide-water systems and of ternary alkali halide-tert-butyl alcohol-water systems have been measured at 25°C in the water-rich region. The relative viscosities of the ternary solution are expressed by an extended form of the Jones-Dole equation $$\begin{gathered} \eta /\eta _0 = 1 + {\text{A}}_E {\text{m}}_E^{1/2} + {\text{B}}_E {\text{m}}_E + {\text{B}}_N {\text{m}}_N + {\text{D}}_{EE} m_E^2 \hfill \\ + {\text{D}}_{NN} {\text{m}}_N^2 + {\text{D}}_{EN} {\text{m}}_E {\text{m}}_N + ... \hfill \\ \end{gathered} $$ wherem _E andm _N are the molalities of the electrolyte E and nonelectrolyte N expressed in mole-kg^?1 of water. The parameterA _E accounts for the long-range ionic forces, andB _E andB _N are the Jones-DoleB coefficients of E and N. It is shown, in particular, that theD _EN term is additive for different ionic pairs and that it can be correlated to the entropic coefficient of pair interaction. TheD _EN coefficients thus seem to reflect some pair interaction contribution to the excess viscosity of ternary mixtures.     

Molecular symmetry. IV. The coupled perturbed Hartree–Fock method

Symmetry methods employed in the ab initio polyatomic program HONDO are extended to the coupled perturbed Hartree–Fock (CPHF) formalism, a key step in the analytical computation of energy first derivatives for configuration interaction (CI) wavefunctions, and energy second derivatives for Hartree–Fock (HF) wavefunctions. One possible computational strategy is to construct Fock-like matrices for each nuclear coordinate in which the one- and two-electron integrals of the usual Fock matrix are replaced by the integral first derivatives. “Skeleton” matrices are constructed from the unique blocks of electron-repulsion integral derivatives. The correct matrices are generated by applying a symmetrization operator. The analysis is valid for many wavefunctions, including closed- or open-shell spin-restricted and spin-unrestricted HF wavefunctions. To illustrate the method, we compare the computer time required for setting up the coupled perturbed HF equations for eclipsed ethane using D_3h symmetry point group and various subgroups of D_3h. Computational times are roughly inversely proportional to the order of the point group.     

Spectroscopic studies of ionic solvation. XXI. A raman,infrared, and NMR study of sodium perchlorate solutions in nonaqueous solvents

Sodium perchlorate solutions in several nonaqueous solvents were examined by²³Na,³⁵Cl-NMR, infrared, and Raman spectroscopic techniques. The formation of contact ion pairs lowers the symmetry of ClO ₄ ^– ion from T_d to C_3v or C_2v provided that the interaction is fairly strong. This was manifested for NaClO₄ solutions in acetonitrile, tetrahydrofuran, and pyridine. Combination of the vibrational measurements with NMR shows that in the above three cases the anion-cation interactions are quite strong. Sodium-23 NMR studies confirm the above results and, being a more sensitive technique, also indicates weak cation-anion interaction in propylene carbonate, formic acid, acetone, methanol, ethanol, dimethyl sulfoxide, and water. In all solvents the²³Na resonance shifts upfield with increasing concentration of NaClO₄, indicating that the replacement of solvent by ClO ₄ ^– ion decreases electron density around the cation.     

FT-IR Investigation of Rare-Earth and Metal-Ion Solvation. Part 14. Interaction between uranyl perchlorate and dimethyl sulfoxide in anhydrous acetonitrile

The interaction between the uranyl ion and perchlorate in anhydrous acetonitrile has been investigated by FT-IR and Raman spectroscopy. Vibrations assigned to uncoordinated (u), monodentate (m), and bidentate (b) perchlorate anions were identified in 0.075M solutions. Quantitative data indicate that perchlorate is distributed as follows: 37 ± 2% are uncoordinated, 36 ± 7% are monodentate, and 27 ± 7% are bidentate. This is in agreement with the conductivity of the solutions which is at the lower end of the range accepted for 1:1 electrolytes. The splittings v₄–v₁(m) and v₈–v₁(b) of 147 and 246 cm^?1, respectively, point to a large inner-sphere interaction. An equilibrium occurs between two differently coordinated species. Various amounts of DMSO were added to 0.05M perchlorate solutions (R′ = [DMSO]_t/[UO]_t = 1–10). The v₇ (SO) and v₂₂ (CS) vibrations of DMSO were used to determine the average number of coordinated DMSO molecules per uranyl ion, which is close to 4. Some bidentate perchlorate ions are still present in these solutions, but all the MeCN molecules (2.6 on average) are expelled out of the inner coordination sphere. The data can again be interpreted in terms of an equilibrium between differently coordinated species. The average coordination number of the uranyl ion is 4.4, as the perchlorate salt in MeCN solution, and may be somewhat smaller in the presence of DMSO. The possible presence of dimeric species is also discussed.     

Conformational behavior of styrene–p-chlorostyrene triblock copolymers in dilute solutions. I. Composition dependence of conformational behavior

Dilute solution properties of (styrene-p-chlorostyrene) triblock copolymers in various solvents were studied over a wide range of molecular weight and composition. Viscosity and osmotic pressure results indicate that the conformational behavior of the B_mA_nB_m and A_mB_nA_m copolymers (A = styrene; B = p-chlorostyrene; m and n denote the number of units) are similar in nonselective solvents such as toluene and 2-butanone, but different in selective solvents such as carbon tetrachloride and cumene. Short-range and long-range interaction parameters of the block copolymers were determined by applying the Stockmayer–Fixman method to viscosity data and also by application of the equation relating the osmotic virial coefficient and the excluded volume. The results show that the unperturbed dimensions of the block copolymers vary linearly with composition, and long-range interaction parameters in nonselective solvents can be expressed by those of the parent homopolymers, the chemical composition, and values of the interaction parameter β_AB between styrene and p-chlorostyrene monomeric units.     

Solute—Solvent interactions in water-rich mixtures. I. Ionic conductances in water—Acetonitrile mixtures at 25°C

Conductance measurements oni-Am₃BuNI (TABI), NaBPh₄, NaI, NaBr, NaCl, and KCl are reported for aqueous mixtures containing up to 20 mole% acetonitrile at 25°C. Experimental data were analyzed by the 1965 Fuoss-Onsager-Skinner equation. Limiting ionic equivalent conductances in water-acetonitrile mixtures were calculated assuming that the contribution to the limiting conductance foriAm₃BuNBPh₄ is the same for both ions involved. The trends observed for the limiting ionic conductance-viscosity products for several ions in these water-rich solvents are discussed in terms of structural effects and ion-solvent interaction.