Mikhail Ya. Goikhman

Novel approach to determination of sorption in pervaporation process: a case study of isopropanol dehydration by polyamidoimideurea membranes

Development of novel membranes with optimal performance, selectivity, and stability is a key research area in membrane technology. In the present work aromatic polyamidoimideurea (PAIU) is synthesized and tested as promising membrane material for separation of water and alcohol mixtures. The PAIU membrane structure, density, and transport properties are studied. Mass transfer of water and isopropanol through the membrane is estimated by sorption and pervaporation tests to determine equilibrium sorption degree, diffusion coefficients, flux through the membrane, and separation factor. Two techniques of sorption study from liquid and from vapor phases are used as novel approach to experimental study of mass transfer. The vapor sorption calorimetry permits to analyze the behavior of the polymer material in sorption process. In pervaporation of water–isopropanol mixture, almost pure water mainly permeates through PAIU membrane. To improve the performance, a double layer membrane containing a thin PAIU layer on the surface of porous poly(phenylene oxide) support is developed. The double layer membrane is extremely effective in dehydration of isopropanol.

Polymer biquinolyl-containing complexes of Pd(II) as efficient catalysts for cyanation of aryl and vinyl halides with K4Fe(CN)6

A catalytic system for cyanation of aryl and vinyl halides with K4Fe(CN)6 based on a structurally tunable and nontoxic polymer backbone of polyamic type with biquinolyl fragments in the polymer chain capable of coordination to PdII ions is developed. The catalyst is eligible for thermal and microwave activation; in the latter case the reaction time is dramatically decreased. Cyanation of vinyl bromides occurs stereoselectively, and the configuration of the starting alkene is retained; even for Z-isomers the impact of configuration inversion is less than 5%. The polymer-based Pd catalyst is applicable for one-pot multi-step synthesis of the precursors of mesogenic structures of biphenyl type. Consecutive cross-coupling and cyanation reactions can be performed in the presence of the same portion of catalyst, in the same solvent, without isolation of intermediate products.

Aromatic Copolyamides with Anthrazoline Units in the Backbone: Synthesis, Characterization, Pervaporation Application

Copolyamides with anthrazoline units in the backbone (coPA) were synthesized and dense nonporous films were prepared by solvent evaporation. Glass transition temperature, density, and fractional free volume were determined for the dense nonporous films composed of polyamide and two of its copolymers containing 20 and 30 mol % anthrazoline units in the backbone. Transport properties of the polymer films were estimated by sorption and pervaporation tests toward methanol, toluene, and their mixtures. An increase in anthrazoline fragments content leads to an increasing degree of methanol sorption but to a decreasing degree of toluene sorption. Pervaporation of a methanol–toluene mixture was studied over a wide range of feed concentration (10–90 wt % methanol). Maximal separation factor was observed for coPA-20 containing 20 mol % fragments with anthrazoline units; maximal total flux was observed for coPA-30 with the highest fractional free volume.

Electrochemical Formation of the Redox-Active Metal-Containing Polymers for Catalytic and Electrocatalytic Applications

A convenient electrochemical approach to new redox-active Cu, Pd, Ni -containing polymers of polyamic type with biquinoline (biQ) fragments was elaborated. The comparative analysis of the data obtained revealed the main factors which influence the type of metal coordination unit formed in the polymer: the nature of metal, the number of biQ fragments and conformational rigidity of the polymer backbone as well as the electrolysis conditions. Voltammetric investigation of metal-polymers allows distinguishing the types and relative amounts of metalcoordination units formed. The comparison of the electrochemical data with the results of catalytic tests revealed the guidelines for electrochemical synthesis of efficient catalytic systems.

Improvement of Selective Properties of Waveguide Bragg Resonators

A method to improve the selective properties of a waveguide resonator with Bragg reflectors on its ends is investigated. It is shown that additional mode conversions lead to a significantly rarefied spectrum of eigenoscillations. This can be achieved by using doubly periodic Bragg reflectors with different azimuthal symmetries forming four wave resonant field structures. The analysis of the dispersion properties is presented and is applicable for resonators of arbitrary relation of lengths of the reflectors and waveguide.