Alternating copolymers of hexafluoroisobutylene with vinyl trifluoroacetate and vinyl pentafluorobenzoate

Copolymerizations of hexafluoroisobutylene (HFIB) with vinyl pentafluorobenzoate (VPFB) and vinyl trifluoroacetate (VTFA) were carried out in bulk using perfluorodibenzoyl peroxide as the radical initiator. The copolymers obtained were characterized by proton and fluorine NMR spectroscopy. The monomer reactivity ratios in the polymerization of HFIB with VPFB were r₁ (HFIB) = 0, r₂ (VPFB) = 0.373, and r₁r₂ = 0. The results indicated that these copolymers have alternating structures. Similarly, the copolymers of HFIB and VTFA also showed alternating structures. The films of HFIB‐co‐VPFB were prepared by casting THF solution of polymers. Films obtained were flexible and transparent. The refractive indices of copolymers were 1.4549, 1.4490, and 1.4438 at 532, 633, and 839 nm, respectively. The average T_gs of HFIB‐co‐VTFA and HFIB‐co‐VPFB were 52 and 71 °C, respectively. From these results, the T_g of the hypothetical HFIB homopolymer is postulated to be in between 70 and 90 °C, which may be useful in the assessment of T_gs of HFIB copolymers with other vinyl monomers. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Numerical study of QCD phase diagram at high temperature and density by a histogram method

We study the QCD phase structure at high temperature and density adopting a histogram method. Because the quark determinant is complex at finite density, the Monte-Carlo method cannot be applied directly. We use a reweighting method and try to solve the problems which arise in the reweighting method, i.e. the sign problem and the overlap problem. We discuss the chemical potential dependence of the probability distribution function in the heavy quark mass region and examine the applicability of the approach in the light quark region.     

Preparation of polymethyl methacrylate with well-controlled stereoregularity by anionic polymerization in an ionic liquid solvent

This study investigates the effect of ionic liquids (ILs) on the anionic polymerization of methyl methacrylate (MMA). Polymethyl methacrylate (PMMA), an isotactic polymer, is prepared by anionic polymerization at a high reaction temperature with an IL that acts as both solvent and additive. The most plausible reaction mechanism is determined using ¹H NMR and Fourier-transform infrared spectroscopy. The electrostatic interaction between MMA and the IL increases the apparent steric hindrance in MMA, resulting in the isotactic PMMA.     

Structures and Reaction Mechanism of Novel Metal-Carbene Complexes Derived from Hypervalent Diazadiselenathiapentalenes

Abstract

Novel metal-carbene complexes (4) with a metallapentalene framework have been obtained from hypervalent diazadiselenathiapentalenes (3) by treating with Pt(PPh₃)₄, Pd(PPh₃)₄ and RhCl(PPh₃)₃. X-Ray investigations revealed that the central hypervalent sulfur atom in 3 was substituted by a metal atom to form M-Se bonds in the resultant metallapentalene framework.     

Free-surface roughness of thin-walled tubes in reduction

The problem of the stress-strain state of thin-walled tubes in axisymmetric steady-state deformation is solved using the membrane theory of shells and the model of an ideal rigid-plastic material satisfying the Mises yield condition and the associated flow law. The obtained solution is used together with the empirical relation between the strain state at an arbitrary point of the free surface and the surface roughness parameters at the same point to determine the influence of some tube reduction parameters on the surface roughness parameters in the product. The employed empirical relation is derived assuming that the free surface roughness parameters depend on two independent kinematic variables.     

REACTION OF SULFUR CHLORIDE WITH ACETOPHENONE. II

Abstract

In a previous paper,¹ we reported the formation of a resinous material (1) from the reaction of sulfur chloride with acetophenone which, upon treatment with DMF, yielded phenylglyoxylthiodimethylamide (4). We now report two additional resinous materials (5, 6), resulting from bromination of sodium phenacylthiosulfate (3) and diphenacyl disulfide (7) respectively, both of which not only resemble resinous 1 in appearance, but also yield 4 upon treatment with DMF in aqueous alkali.

Resinous 1, 5, and 6 appear to have the same common basic structure and differ only in the number of sulfur atoms bonded between the common units. Cleavage at the sulfur-sulfur bonds and elimination of hydrogen halide then yields identical oxothioamides from 1, 5, or 6. The latter appears to be a general reaction, and several oxothioamides were prepared by this synthetic method from 1, 5, and 6 and various amides and amines.