Photoinitiated cationic polymerization by dialkylphenacylsulfonium salts

Dialkylphenacylsulfonium salts in which the anions are of the general type BF, AsF, PF, and SbF are a new class of useful photoinitiators for cationic polymerization. On irradiation these salts underwent reversible ylid formation with the simultaneous generation of strong Br?nsted acids. The photoinitiated cationic polymerization of a number of monomers with dialkylphenacylsulfonium salts demonstrated the utility of these new photoinitiators.     

Photoinduced electron transfer from polystyrene pendant tris(2,2′-bipyridyl)ruthenium (II) complex to methylviologen

The characteristics of the photoinduced electron transfer reaction from polystyrene pendant tris(2,2′-bipyridyl)ruthenium (II) complex [Ru(bpy)] to methylviologen (MV²⁺) were studied. The rate constant k₁ from the excited state of the complex, Ru(bpy), to MV²⁺ were determined for both the polymeric and monomeric complexes from the lifetime τ of Ru(bpy) and the quenching rate of Ru(bpy) by MV²⁺. The polymer pendant Ru(bpy) showed three kinds of τ components ranging from 7 to 474 ns, in contrast to the monomeric complex, which showed one component of 350 ns. The k₁ values for both complexes were almost the same, on the order of 10⁸ L/mol s. The photoinduced electron transfer from solid-phase Ru(bpy) to liquid-phase MV²⁺ was realized by utilizing the polymer complex, and the solid–liquid interphase reaction system is discussed.     

Photoinitiated cationic polymerization by triarylselenonium salts

Triarylselenonium salts with complex metal halide anions such as BF, AsF, and SbF have been prepared and have been shown to be efficient photoinitiators of cationic polymerization. The photolysis rates of these compounds were studied and their quantum yields of photolysis were reported. Use of specific triarylselenonium salts in the polymerizations of cyclohexene oxide, epichlorohydrin, and 2-chloroethyl vinyl ether are described.     

Kinetics and mechanism of the cationic polymerization of tetrahydrofuran in solution. THF–CH2Cl2 and THF–CH2Cl2/CH3NO2 systems

Cationic polymerization of tetrahydrofuran (THF) in CH₂Cl₂ solvent and in mixed CH₂Cl₂/CH₃NO₂ solvent was initiated with 1,3-dioxolan-2-ylium cations with AsF and SbF anions. Dissociation constants of the polytetrahydrofuranium ion pairs into ions were measured (e.g., K_D = 1.5 × 10^?5M at 25°C and [THF]₀ = 7.0M; CH₂Cl₂ solvent) and were found to be more than 100 times lower than in CH₃NO₂ solvent at the same [THF]₀ and temperature. The rate constants k and k, measured for degrees of dissociation ranging from 0.03 to 0.35 in CH₂Cl₂, were the same within an experimental error of measurements (±15% of the value of k_p). Dependence of k( = k = k) on the dielectric constant was a monotonous function in three different solvents, namely, CCl₄, CH₂Cl₂, and CH₃NO₂, which covered a large range of dielectric constants of the medium (from D = 5 to D = 22) and degrees of dissociation of the macroion pairs, α (from 0.03 to more than 0.70). Thus a decrease in the dielectric constant increases the rate constant k in the whole range of studied polarities of the medium. This result confirms an earlier conclusion that the rate constant of propagation does not depend on the state of aggregation of ions and k = k.     

Kinetics and mechanism of the cationic polymerization of tetrahydrofuran in solution: THF-CH3NO2 system

Polymerization of tetrahydrofuran (THF) in CH₃NO₂ solvent was initiated with 1,3-dioxolan-2-ylium cations with AsF and SbF anions, as well as with esters of FSO₃H and CF₃SO₃H acids. Polymerization shows in this solvent a living feature: values of k_p (determined directly from the semilogarithmic kinetic plots) were the same for all of the listed above initiators; thus k_p is the same for AsF, CF₃SO, FSO, and SbF anions. The identity of the k_p values for complex and noncomplex (ester-forming) anions comes from the fact that in CH₃NO₂ solvent equilibrium between macroesters and macroion pairs is shifted almost completely (K_e = 33.0 at 25°C and |THF|₀ = 7.0M) to the macroions side. Dissociation constants of the polytetrahydrofuranium ion pairs (CF₃SO and SbF anions) were measured (e.g., K_D = 2 × 10^?3 M at 25°C and |THF|₀ = 7.0M; i.e., at D = 22.8, ΔH_D = ?3.8 ± 6 kcal mole; ΔS_D = ?25 ± 2 eu). On the basis of the known values of K_D, and therefore dissociation degrees α, rate constants of propagation on the free and paired THF cations (k and k) were determined for a large range of degrees of dissociation (α from 0.15 to 0.52). The rate constants k and k were found to be the same within an experimental error of measurements (± 15% of the value of k_p). Apparently, the polytetrahydrofuranium cations are highly solvated or even separated from their anions by molecules of THF itself. At these conditions the reactivities of the solvated “free” and solvated (or separated) paired cations became undistinguishable.     

Gamma radiation-initiated polymerization of styrene at high pressure. III. Emulsion polymerization with anionic emulsifiers

Values calculated for the activation volume for chain propagation, ΔV, for the polymerization of styrene in emulsions under a variety of conditions agree closely with that previously obtained in pure styrene (ΔV = ?18.6 cm³ mol^?1). The rate of initiation of emulsion polymerization by radicals produced in the water phase was independent of pressure; therefore ΔV is zero. This differs from initiation in pure styrene which is slightly retarded by pressure (ΔV = 2.0 cm³ mol^?1). The activation energy for the reaction in emulsion, as in pure monomer, decreases slightly with pressure. Chain transfer to monomer occurs to a much greater extent in emulsions than in pure monomer under similar temperature and pressure conditions. Values for the dependence of the polymerization rate on the initiator (i.e., the irradiation dose rate) and emulsifier concentration are consistent with Smith–Ewart, Case II kinetics.     

Rigid backbone polymers. XI. Solution phase-viscosity relationship

Using combined results of isothermal viscosity measurements and cross-polarized light microscopy on four polyisocyanate/solvent systems, the following were demonstrated: (a) an anisotropic phase appears, associated with a shoulder in the viscosity curve, at a concentration v lower than the peak viscosity at v; (b) the inversion from anisotropic inclusions in an isotropic matrix to isotropic inclusions in an anisotropic matrix, occurs at concentrations v > v and (c) the attainment of a single phase, microscopically anisotropic, occurs at v > v; where the viscosity is decreasing but has not yet reached its minimum. When the experiments were repeated with changes in temperature, the following were observed: (a) within each single phase the viscosity drops with increased temperature; (b) in the biphasic range, the total viscosity η⁰ remains about constant in the concentration range ≤ and increases with temperature in the range v > v; (c) in the interval v > v of the biphasic range, at constant temperature an increase in concentration decreases η⁰, and at constant concentration, a decrease in temperature lowers η⁰. Qualitative explanations of the observations are proposed.     

Interaction of monovalent and divalent counterions with some carboxylic polysaccharides

Eleven samples of carboxylic polysaccharides were studied. The activity coefficients γ have been measured for monovalent (Na⁺) and divalent (Ca²⁺) counterions. There is no specific influence of the structure of the chain on γ values. Agreement with theoretical values confirms the rigidity of the chain; for low charge density, the theoretical treatment seems to be incorrect. Selectivity is discussed in term of selectivity coefficient K and free energy of exchange ΔG; ΔG is linearly related to the charge density but K which characterizes the competition of the two counterions is sensitive to the nature of the chain. The carboxymethylamyloses present a larger selectivity whose origin is not discussed here. The last point treated is the intrinsic constant of dissociation of polyacids. The pK₀ values are practically independent of the nature of the polyelectrolyte and of the charge density; the values are close to the pK₀ of monomeric unit and are not affected by the position of ? COOH in the anhydroglucose ring.     

Relationship of stress to uniaxial strain in crosslinked poly(dimethylsiloxane) over the full range from large compressions to high elongations

Experiments on inflated sheets of crosslinked poly(dimethylsiloxane) covering a sixfold range of compression are combined with measurements in elongation conducted on specimens from the same sample to obtain the relationship of stress to strain over a 24-fold range in the extension ratio λ₁. With increase in λ the reduced force [f] ≡ f(λ₁ – λ)^?1 rises to a maximum near λ = 1.2–1.4, then decreases very slowly with further increase in λ. The form of the relationship of [f] to λ confirms recent theory.     

The role of d orbitals in tetrahedral hybrid orbitals of oxy-ions

The hybrid orbitals of tetrahedral oxy-ions containing some d character have been calculated by maximum overlap method. The d characters of hybrid orbitals increase in the order of SiO, PO, SO, ClO, and decrease in order of GeO, AsO, SeO, BrO. The bond strengths are also obtained for these ions. The hybrid Orbital of VO, CrO, and MnO are of the type d³s as the result of calculation.     

Modification of properties of ion exchange membranes. VI. Electrodialytic transport properties of cation exchange membranes with a electrodeposition layer of cationic polyelectrolytes

When a cation exchange membrane is immersed in a cationic polyelectrolyte solution to form a thin layer on the membrane surface, the membrane properties are changed: permselectivity between cations with different electric charges (a relative transport number of the calcium ions to sodium ions, P), current efficiency, and electric resistance of the membrane. Here the more compact the cationic polyelectrolyte layer, the more outstanding the change in permselectivity. To make a more compact layer, an electrodeposition method was adopted and a change in the permselectivity of the resultant cation exchange membrane was investigated. By using the electrodeposition method a strongly basic polyelectrolyte with a larger molecular weight effectively changed the permselectivity of the cation exchange membrane: the P value dropped to about 0.3 from about 2.5 of the P of the untreated membrane during electrodialysis of the sodium chloride—calcium chloride system, and an increase in the electric resistance of the membrane (i.e., organic fouling) due to a cationic surface-active agent could be prevented. It is noteworthy that by using the strongly basic polyelectrolyte with a larger molecular weight the electrodeposition method was effective, whereas the immersion method was ineffective. Furthermore, even with the electrodeposition method the cationic polyelectrolyte which had a relatively smaller molecular weight resulted in a more remarkable change in the P value than did that with a larger molecular weight. In the electrodeposition method the amount of polyelectrolyte cohered onto the membrane surface in creased with an increase in the concentration of the polyelectrolyte, and weakly basic polyelectrolyte, and weakly basic polyelectroyte (polyethyleneimine) was also available independent of its molecular weight.     

Cationic grafting from carbon black. II. Polymerization of styrene initiated by CO+ClO group on the surface of carbon black

The cationic grafting of polystyrene initiated by carbon black containing the CO⁺ClO group was investigated. The introduction of CO⁺ClO groups onto a carbon black surface was achieved by the reaction of AgClO₄ with carbon black that contained a COCI group. The latter was introduced by the reaction of carboxyl groups with SOCl₂. It was found that polystyrene chains could be grown from CO⁺ClO groups on the surface of carbon black. Moreover, polystyrene was effectively grafted from carbon black: the grafting ratio at 20°C increased to 58% as conversion increased. Furthermore, the grafting ratio and molecular weight of ungrafted polystyrene decreased with an increase in polymerization temperature. These results were explained by the fact that the increasing temperature of the polymerization caused an increase in the rate of chain transfer reaction of the growing polymer chain to the monomer. The carbon black obtained from the reaction produced a stable colloidal dispersion in a good solvent for polystyrene.     

Über geordnete Perowskite mit Kationenfehlstellen. XI. Verbindungen vom Typ ABB□1/4WVIO6 ≙ ABIIB□WO24 mit AII,BII = Ba,Sr

On Ordered Perovskites with Cationic Vacancies. XI. Compounds of Type A B B □_1/4W^VIO₆ ? A B^IIB □W O₂₄ with A^II, B^II = Ba, Sr Depending on the ionic radii of the two and three valent cations in the perovskites of type ABB □_1/4W^VIO₆ ?; AB^IIB □WO₂₄ order disorder phenomena are present. The results of the x-ray and vibrational spectroscopic investigations as well as the diffuse reflectance spectra and the visible photoluminescence are reported.     

γ-radiation-initiated polymerization of bulk styrene at high pressure

The polymerization of styrene in bulk at pressures up to 273 MPa and temperatures between 3 and 49°C with the use of γ-radiation as the initiator has been studied. The polymerization rate and the molecular weight of the polymer increased with increasing pressure; the molecular weight increased at a slightly faster rate. The difference in the rate is a theoretical expectation which has not previously been observed because chain-transfer reactions obscure the effect in chemically initiated systems. A small but significant retardation of the initiation reaction occurs as the pressure is increased. The results of previous workers are critically reviewed. Chain transfer at 25°C for pressures below 220 MPa is negligible when γ-radiation is the initiator. The activation energy for bulk polymerization decreased with increasing pressure from 28.1 kJ/mole at 0.1013 MPa to 22.3 kJ/mole at 203 MPa. Volumes of activation at 25°C for 0.1013 < p < 273 MPa were calculated to be Initiation, +4.0 < ΔV < +4.4 cm³/mole; polymerization; ?Δ = ?20.9 cm³/mole; degree of polymerization; ΔV = ?25.3 cm³/mole; propagation/termination; ?ΔV = ?22.7 cm³/mole.     

Asymmetric polymerization of triphenylmethyl methacrylate by optically active anionic catalysts

Triphenylmethyl methacrylate (TrMA) was polymerized with two types of asymmetric anionic catalyst, lithium (R)-N-(1-phenylethyl)anilide (LiAn) and (-)-sparteine–butyllithium complex (Sp–BuLi), at ?78°C. Both catalysts yielded optically active polymers. The polymers obtained with LiAn in toluene and tetrahydrofuran (THF) showed specific rotations [α] of from ?50° to ?90° (in THF). The [α] of the polymer obtained with Sp–BuLi in toluene was positive and increased with polymer yield reaching above +300°s, whereas the polymer obtained in THF showed a low [α] (ca. +7°). Gel permeation chromatograms of both polymers obtained with LiAn and Sp–BuLi in THF exhibited rather narrow molecular weight distributions, whereas those obtained in toluene showed at least two or three components with markedly different molecular weights. The circular dichroism (CD) spectrum of the polymer obtained with Sp–BuLi showed strong positive peaks at 208 and 232 nm and a weak band at 250–280 nm; the polymer produced with LiAn showed a similar spectrum with opposite sign. The poly(methyl methacrylate)s derived from these poly(TrMA)s were highly isotactic but showed negligible rotations ([α] ± 2° in toluene). The polymer of high molecular weight showed clear polarization under a polarizing microscope and the low polymer obtained with LiAn appeared to show flow birefringence in chloroform at room temperature.     

Zur Kristallstruktur von OMF (M = Sb,Ru, Pt,Au)

On the Crystal Structure of O MF (M = Sb, Ru, Pt, Au) OMF (M = Sb, Ru, Pt, Au) were obtained again, but for the first time investigated by X-ray methods. Colourless OSbF and the rubyred compounds ORuF and OPtF crystallize isostructural in space group Ia3 -T_h⁷ (Nr. 206) with a = 1016(1) pm (Sb), a = 1002.6(9) pm (Ru) and a = 1003.6(9) pm (Pt), Z = 8. Yellow OAuF crystallizes trigonal-rhombohedric in space group R3 -D₃₂⁶ (Nr. 148) with a = 775.9(3) pm, c = 711.7(4) pm, Z = 3.     

The reactions of polyacetylene with trimethyloxonium hexachloroantimonate. Covalent doping of (CH)x

Polyacetylene, (CH)_x, has been doped with trimethyloxonium hexachloroantimonate, (CH₃)₃O⁺SbCl(1), in dichloromethane and acetonitrile. The maximally doped (CH)_x films have moderate conductivities [σ_RT(CH₂Cl₂) = 10, σ_RT(CH₃CN) = 0.7 Ω^?1 cm^?1]. Reactions between 1 and (CH)_x CH₂Cl₂ or CH₃CN were followed in situ by ¹H nuclear magnetic resonance spectroscopy and x-band electron spin resonance spectroscopy. It was found that the reactions in the two solvents are different. In dichloromethane the dopant is SbCl₅, which forms from the decomposition of 1, and doping proceeds by electron removal from (CH)_x chains. Based on the ESR signal loss, an estimate can be made of the diffusion rate of SbCl₅, into the (CH)_x fibrils in CH₂Cl₂; it is found to be ca. 10^?17 cm²/s. In acetonitrile the dopant appears to be either CH₃CNCH, H⁺, CH, or a combination of one or more of these dopants. It is postulated that the CH₃CNCH, CH, and/or H⁺ dopant covalently binds to the (CH)_x chain. X-ray photoelectron spectra show that films doped with excess 1 in both solvents have approximately one SbCl per 33 CH units.     

Effect of isotopic composition on free-radical reactions in polyolefins

On substitution of hydrogen by deuterium the radiation yield of free radicals in polyolefins decreases ca. 2-fold. Under ultraviolet illumination (γ < 300 nm) in deuterated polyethylene (DPE), allyl radicals are converted into alkyl radicals (hfs constants a = 3.2 Oe, a = 4.4 Oe); in deuterated polypropylene (DPP), allyl and peroxide radicals are converted into alkyl radicals (a = 3.7 Oe). At 77°K under ultraviolet light in γ-irradiated polyethylene (PE) and DPE, triene, tetraene, dienyl, trienyl, and tetraenyl radicals are formed. Deuterium substitution has no effect on absorption spectra of polyenyl radicals and polyenes. In polyolefins the quantum yields of photochemical reactions of allyl and peroxide radicals are 0.1–1.0. Photochemical reactions of peroxide radicals result in a radical concentration increase of ca. 3-fold. In reactions of peroxide radicals in the dark, a kinetic isotope effect has been observed. Activation energies of substitution reactions of peroxide radicals are in PE, 9.3 ± 0.3 kcal/mole; in DPE, 10.2 ± 0.3 kcal/mole; in PP, 12.7 ± 0.4 kcal/mole; in DPP, 14 ± 0.5 kcal/mole. Possible mechanisms of the effect of polyolefin isotope composition on radical formation by high energy irradiation as well as on photochemical and dark reactions of free radicals are discussed. The effect of the energy released from phototransformations and radiationless deactivation of macroradicals on the migration of free valence is also considered.     

Charge stripping C

Measurements of the translational energy loss accompanying the charge-stripping reactions M⁺+N→M²⁺+N+e⁻ and M²⁺+N→M³⁺+N+e⁻ have been performed for C, C and C, C respectively. The energy nesessary to remove the second electron from Buckminsterfullerene was determined, Q=IE(C→C=12.25±0.5 eV.     

A thermodynamic approach to the stress-induced crystallization in cross-linked rubbers

The thermodynamic treatment of crystallization phenomena in a prestretched rubber was undertaken. Emphasis was put on defining conditions for the thermodynamic stability of the extendedor folded-chain crystal structure. The extended-chain structure is found to be stable thermodynamically at temperatures higher than the isotropic melting point of un-cross-linked polymer T in the stretched state, while the folded chain one is not. Below T, the stretch ratio of the network structure determines which crystal structure is more stable. The relation among the critical stretch ratio for the extended/folded crystalline structure transition, temperature, and molecular weight is also discussed. The crystallinity predicted by this work becomes zero at a temperature of T, the isotropic melting point of a cross-linked system. The value of T decreases with increasing cross-link density, and this is consistent with the experimental data reported in the literature.