Effect of ionic interaction on linear and nonlinear viscoelastic properties of ethylene based ionomer melts

The effect of ionic interaction on linear and nonlinear viscoelastic properties was investigated using poly(ethylene-co-methacrylic acid) (E/MAA) and its ionomers which were partially neutralized by zinc or sodium. Dynamic shear viscosity and step-shear stress relaxation studies were performed. Stress relaxation moduli G(t, y) of the E/MAA and its sodium or zinc ionomers were factorized into linear relaxation moduli G°(t) and damping functions h(y). The relaxation modulus at the smallest strain in each ionomer agreed with the linear relaxation modulus calculated from storage modulus G and loss modulus G. In the linear region, the ionic interaction shifted the relaxation time longer with keeping the same relaxation time distribution as E/MAA. In the nonlinear region, the ionic interaction had no influence on h(y) when the ion content was low. At higher ion content, however, the ion bonding enhanced the strain softening of h(y).     

Poly(ethylene oxide) thin films produced by electrospray deposition: morphology control and additive effects of alcohols on nanostructure

Nanostructured thin films were prepared by electrospray deposition (ESD) from poly(ethylene oxide) (PEO) aqueous solution. The surface morphologies of the deposited films were observed using scanning electron microscopy (SEM). The SEM images revealed the correlations between the morphologies and the ESD conditions. By changing the applied voltage and solution properties such as viscosity, surface tension, conductivity, and molecular weight, PEO thin films with diverse nanostructures--from nanospheres to nanofibers--were fabricated. It was also revealed that the addition of alcohols to polymer solution, which enables simultaneously changing the viscosity, the surface tension, and the conductivity, enhanced the formation of the fibrous structure. These results indicate that the ESD method is potentially a useful option for producing nanoengineered polymer surface.     

Mechanism of stereo- and regioselectivity in the Paternò-Büchi reaction of furan derivatives with aromatic carbonyl compounds: importance of the conformational distribution in the intermediary triplet 1,4-diradicals

Temperature and substituent effects on the stereo- and regioselectivity have been investigated in the photochemical [2 + 2] cycloaddition reaction, the so-called Paternò-Büchi (PB) reaction, of unsymmetrically substituted furans 2a,b (2-methyl- and 3-methylfuran) with aromatic carbonyl compounds 1a,b (benzaldehyde and benzophenone). The regio-random but stereoselective (exo/endo > 97/3) formation of lower substituted oxetane 3a and higher substituted oxetane 4a is found in the reaction with benzaldehyde (1a). The exclusive stereoselectivity is not dependent on the position of methyl substituent on the furan ring and the reaction temperature. The double-bond selection (3a versus 4a) is slightly dependent on the reaction temperature (3a/4a = 55/45 to 40/60). The Eyring plots of the regioselectivity are linear. Contrastively, in the reaction with benzophenone (1b), the double-bond selection (3b versus 4b) largely depends on the reaction temperature. The Eyring plots are not linear, but the inflection points are observed. The transient absorption spectroscopic analyses (picosecond time scale) clarify the intervention of triplet 2-oxabutane-1,4-diyls in the photochemical processes. Computational studies reveal the equilibrium structures of the triplet diradicals, energy barriers between the conformers, and the equilibrium constants. A rational mechanism is herein proposed by the support of both experimental and computational investigations to account for not only the exclusive formation of the exo-configured oxetanes 3a and 4a but also the nonlinear Eyring plots observed in the reaction with 1b.     

Nucleophilic addition to 3,4-cis-diacetyl-1,2,3,4-tetramethyl-1-cyclobutene: remarkably fast intramolecular hemiketalization

Reduction of 3,4-cis-diacetyl-1,2,3,4-tetramethyl-1-cyclobutene 1 with NaBH₄ yielding 2-hydroxyoxolanes 2a and 2b with complete diastereoselectivity at the anomeric carbon atom suggests that a highly stereoselective intramolecular hemiketalization process leading to the formation of the 2-hydroxyoxolane unit is much faster than the attack of the second molecule of the nucleophile on the second carbonyl group. Further reduction of 2a at 0 °C gives selectively the meso-diol 3a. Reaction of 1 with MeLi or MeMgBr also involves the participation of the adjacent carbonyl, thereby yielding hydroxyoxolane 5a selectively. A mechanistic rationale is proposed on the basis of the relative energies of all isomeric hemiketals, 2a-d and 5a and b, (calculated by the PM3 method) and the relative stabilities of the conformers of 1 (calculated by the MM2 method).     

Simulations of polymer crystallization under high pressure

High pressure crystallization of polypropylene was studied by means of PVT measurements and computer simulations. The isothermal crystallization behaviour were described by using a model which takes into account the effect of pressure on the temperature dependence of nucleation rate and linear growth rate. The agreement between the simulation and the experiments was seen in the tendency that the crystallization was accelerated by the high pressure. The non-isothermal crystallization behavior was also simulated by applying a generalized Avrami equation. The simulation curves well reproduced the experimental values below relative crystallinity 0.5 and below 100 MPa.     

Direct alkenylation of arylamines at the ortho-position

Treatment of magnesium alkylidene carbenoids, which were generated from 1-chlorovinyl p-tolyl sulfoxides with isopropylmagnesium chloride at −78 °C in toluene, with N-lithio arylamines gave ortho-alkenylated arylamines in moderate to good yields. The reaction was found to proceed in a highly stereospecific manner at the carbenoid carbon. This reaction offers a quite novel and direct alkenylation of arylamines at the ortho-position of the aromatic ring.     

Thermal dehydrations

The behaviour of thermal dehydrations of isomorphous complexes of calcium copper acetate hexahydrate, CaCu(CH₃CO₂)₄·6H₂O and calcium cadmium acetate hexahydrate, CaCd(CH₃CO₂)₄· 6H₂O was studied by means of thermal analyses and X-ray structural analysis. The enthalpy changes for the dehydration of CaCu(CH₃CO₂)₄·6H₂O and CaCd(CH₃CO₂)₄·6H₂O were 315±9.7 and 295±8.0 kJ mol^–1, respectively. The DSC curves of the dehydrations indicated that the seemingly simple dehydrations are more complex than they appear at first sight. Apparent activation energies for the dehydrations of CaCu(CH₃CO₂)₄·6H₂O and CaCd(CH₃CO₂)₄·6H₂O were 85.7±7.4 and 87.9±12.5 kJ mol^–1, respectively.The authors wish to express their thanks to Associate Professor Yasuhiko Yukawa of the Niigata University for the analysis of the X-ray-intensity data.     

The oxidation of s-triazolo[4,3-b]pyridazines with selenium dioxide

Some s-triazolo[4,3-b]pyridazines were oxidized to 2,3-dihydro-s-triazolo[4,3-b]pyridazin-3-ones with selenium dioxide in nitrobenzene at 160–165° (external temperature) for 1–2 hours in 30–40% yields.     

Organic/inorganic hybrid nano-microstructured coatings on insulated substrates by electrospray deposition

Organic/inorganic hybrid nano-microstructured coatings on insulated polymer films were prepared by electrospray deposition (ESD) from an acrylic resin/silica sol blend solution. The surface morphologies of the coated films were observed using scanning electron microscopy (SEM). The SEM images showed that a nano-microscaled fibrous structure was formed on the film. The fiber diameter decreased from 4.4 microm to 600 nm with the increase in the silica sol content. Energy-dispersive X-ray analysis also revealed that silica atoms were homogeneously distributed in the fibrous structure on the polymer film. These results indicated that the ESD method is potentially a useful option for producing nano-microstructured coatings on not only conductive, but also insulating surfaces.