Addition of tert-Butylamine to Diethyl Alkynephosphonates Catalyzed by CuCl

Russian Journal of General Chemistry -     

Spontaneous change in thermosensitive properties of aqueous solutions of poly(<Emphasis Type="Italic">N,N</Emphasis>-dimethylaminoethyl methacrylate) and its mixtures with sodium dodecyl sulfate

It is shown that the properties of aqueous solutions of poly(N,N-dimethylaminoethyl methacrylate) are unstable over time: the pH value spontaneously decreases, the phase separation temperature grows, and the light scattering ability of dispersions arising above the said temperature weakens. These effects are enhanced after dilution of solutions, become less pronounced with an increase in pH, and disappear when the solutions are isolated from atmosphere (under argon). It is inferred that the lability of the indicated properties is associated with acidification of polymer solutions due to their interaction with air carbon dioxide and the enhancement of protonation of macromolecules. Potentiometric and tensiometric measurements have demonstrated that upon introduction of sodium dodecyl sulfate into solutions of poly(N,N-dimethylaminoethyl methacrylate), the surfactant-polymer interaction slows down owing to a spontaneous increase in the charging of macromolecules in the course of time.     

Reaction of Aminoethynylphosphonates with Primary Aromatic Amines

Addition of primary aromatic amines to aminoethynylphosphonates proceeds chemo-and regio-selectively without an acidic catalyst and affords unsymmetrical phosphonoacetamidines. The probable reaction mechanism involves amine addition followed by prototropic isomerization. The method described extends the range of synthetic approaches to various unsymmetrical phosphorylated amidines. Reaction of the starting aminoethynylphosphonates with primary aliphatic amines possessing bulky substituents results in quantitative formation of the corresponding diaminoethynylphosphonates. The structure of the obtained compounds was proved by ¹H, ¹³C, and ³¹P NMR spectroscopy.__________Translated from Zhurnal Obshchei Khimii, Vol. 75, No. 1, 2005, pp. 5–10.Original Russian Text Copyright © 2005 by Panarina, Aleksandrova, Dogadina, Ionin.     

MWA and scanning-probe study of argon-ion irradiation effects on superconducting properties of Bi2Sr2CaCu2O8 thin films

Bi₂Sr₂CaCu₂O₈ films with thickness of 200 and 800 nm were irradiated with monovalent argon ions with an energy of 40 keV and a dose ranging between 10¹⁴ and 10¹⁷ ion/cm². The dose dependences of (i) the superconducting transition temperature, (ii) the critical current density value and (iii) the irreversibility line position on the magnetic field-temperature phase diagram were determined for two series of samples of different thickness. Atomic force microscopy images of the irradiated samples showed an appearance of defects in the form of surface holes. The obtained data were used to establish conditions for improving properties of thin-film superconducting materials. Firstly, the irradiation dose should be at least 10¹⁶ ion/cm² to form embedded gas bubbles and surface holes serving as artificial pinning centers. Secondly, the film thickness and the average depth of the defect formation should be of a comparable value and sufficiently exceed the thickness of the surface layer sputtered as a result of irradiation.     

Addition of Secondary Amines to Alkynephosphonates

Addition of secondary amines to diethyl alkynephosphonates, catalyzed by Cu(I) salts, proceeds regio- and stereospecifically and yields diethyl (E)-2-diethylaminooalkenephosphonates. The E configuration was established by analysis of the vicinal coupling constants between the phosphorus and carbon nuclei in the ¹³C NMR spectra of the reaction products and model compounds: ³ JPC is 6-10 Hz at the cis arrangement of the coupled nuclei and 16 Hz or higher at the trans arrangement. In all the diethyl diethylaminoalkenephosphonates obtained, ³ JPC is about 5 Hz, suggesting cis addition.     

Features of FMR spectra observed in granular films formed by Fe+ implantation into PMMA

Magnetic phase consisting of α-Fe particles arranged in a thin near-surface layer has been synthesized in modified phosphorus-containing polymethylmethacrylate by Fe⁺ implantation at an energy of 40 keV with a dose of 1.2⊙10¹⁷ ion/cm². The spectrum of magnetic resonance of the obtained samples is a superposition of a wide anisotropic absorption line and a set of reproducible lowintensity noiselike signals registered in a wide range of magnetic field. It has been established that a wide absorption line is due to particle conglomerates (larger than 200 nm), each behaving as a thin ferromagnetic film. Noiselike lines can be explained as resonance signals from separate oblate/prolate nanoparticles (50–200 nm in size) randomly oriented with respect to the irradiated surface. Such complicated nanostructures can be formed at an appropriate combination of properties of a polymer matrix, types of bombarded ions and implantation regimes.     

An Effect of Irradiation with Trivalent Boron Ions on Pinning in Bi<Subscript>2</Subscript>Sr<Subscript>2</Subscript>CaCu<Subscript>2</Subscript>O<Subscript>8</Subscript> Thin Films as Revealed by MWA and Hall-Probe Measurements

Bi₂Sr₂CaCu₂O₈ thin films 200 nm thick were irradiated with 120 keV trivalent boron ions with the dose ranging from 10¹¹ to 10¹⁴ ion/cm². The critical parameters of the samples prior and after irradiation were monitored by non-resonance modulated microwave absorption and Hall-probe techniques. For low doses of 10¹¹–10¹² ion/cm², a slight increase in the critical current density and expansion of the area of the non-dissipative transport current flow were revealed. Such results are explained by the formation of separate areas of displaced atoms, which serve as effective pinning centers. The positive effects of irradiation faded away with dose increase of up to 10¹³–10¹⁴ ion/cm². This is due to overlap of radiation-induced defects and weak pinning on them.