Thermally Crosslinkable and Chemically Modifiable Aromatic Polyesters Possessing Pendant Propargyloxy Groups

New aromatic (co)polyesters containing pendant propargyloxy groups were synthesized by phase transfer‐catalyzed interfacial polycondensation of 5‐(propargyloxy)isophthaloyl chloride (P‐IPC) and various compositions of P‐IPC and isophthaloyl chloride with bisphenol A. FTIR and NMR spectroscopic data, respectively, revealed successful incorporation of pendant propargyloxy groups into (co)polyesters and formation of (co)polyesters with desired compositions. (Co)polyesters exhibited good solubility in common organic solvents such as chloroform, dichloromethane, and tetrahydrofuran and could be cast into transparent, flexible, and tough films from chloroform solution. Inherent viscosities and number average molecular weights of (co)polyesters were in the range 0.77–1.33 dL/g and 43,600–118,000 g/mol, respectively, indicating the achievement of reasonably high‐molecular weights. The 10% weight loss temperatures of (co)polyesters were in the range 390–420 °C, demonstrating their good thermal stability. (Co)polyesters exhibited T_g in the range 146–170 °C and T_g values decreased with increase in mol % incorporation of P‐IPC. The study of non‐isothermal curing by DSC indicated thermal crosslinking of (co)polyesters via propargyloxy groups. The utility of pendant propargyloxy group was demonstrated by post‐modification of the selected copolyester with 1‐(4‐azidobutyl)pyrene, 9‐(azidomethyl)anthracene, and azido‐terminated poly(ethyleneglycol) monomethyl ether via copper(I)‐catalyzed Huisgen 1,3‐dipolar cycloaddition reaction. FTIR and ¹H NMR spectra confirmed that click reaction was quantitative. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 588–597     

Study of the peak effect phenomenon in single crystals of 2H-NbSe2

The weakly pinned single crystals of the hexagonal 2H-NbSe₂ compound have emerged as prototypes for determining and characterizing the phase boundaries of the possible order-disorder transformations in the vortex matter. We present here a status report based on the ac and dc magnetization measurements of the peak effect phenomenon in three crystals of 2H-NbSe₂, in which the critical current densities vary over two orders of magnitude. We sketch the generic vortex phase diagram of a weakly pinned superconductor, which also utilizes theoretical proposals. We also establish the connection between the metastability effects and pinning.     

Acceleration of the DABCO-promoted Baylis-Hillman reaction using a recoverable H-bonding organocatalyst

It has been shown that catalytic amounts (20-40 mol %) of bis-aryl (thio)ureas greatly accelerate the DABCO-promoted Baylis-Hillman reaction between a range of aromatic aldehydes and methyl acrylate in the absence of solvent. These robust organocatalysts are superior mole per mole promoters of the reaction than either methanol or water and are recoverable in high yield after the reaction by column chromatography.     

Indecomposable modules over right pure semisimple rings

The aim of this paper is to prove the following result. IfA is a right pure semisimple ring, then it satisfies one of the two following statements:

1. For any positive integern, there are at most finitely many indecomposable right modules of lengthn; or
2. There is an infinite number of integersd such that, for eachd, A has infinitely many indecomposable right modules of lengthd.

The result is derived with the aid of ultraproduct-technique.     

Gas-phase thermolysis of thieno[3,2-e][1,2,4]triazines. Interesting routes towards heterocyclic ring systems

Gas-phase thermolysis of thieno[3,2-e][1,2,4]triazines gave benzonitrile, isothiazole, pyrimidine, [1]benzothieno[2,3-d]pyrimidine and thieno[3,2-d]thiazole derivatives. A mechanism of these pyrolytic transformation was proposed. Two new and efficient syntheses of the starting thieno[3,2-e][1,2,4]triazines were reported.     

Parametric study of the flow and temperature fields in an inductively coupled r.f. plasma torch

A theoretical investigation of the effect of different parameters on the flow and the temperature fields in a radiofrequency inductively coupled plasma is carried out. The parameters studied are: central injection gas flow rate, total gas flow rate, input power, and the type of plasma gas. The results obtained for argon and nitrogen plasmas at atmospheric pressure indicate that the flow and the temperature fields in the coil region, as well as the heat flux to the wall of the plasma confinement tube, are considerably altered by the changes in the torch operating conditions.