Andrzej Jankowski

Reactions of alkali metal macrocyclic complexes: XIX. Reaction of potassium or sodium complexes with oxetane — novel route to organometallic compounds

Abstract Novel reactions of oxetane with K − /K + and Na − /K + complexes in which potassium cation is complexed by 18-crown-6 have been studied. Organometallic alkoxides formed by cleavage of an alkyl—oxygen bond in the oxetane molecule were used for one pot metallation of anisole and triphenylmethane. The reaction with carbon dioxide was also investigated. Reaction mechanisms have been studied by NMR, GLC-MS, IR techniques and chemical analysis.

Surface morphology of the polyurethane-based pervaporation membranes studied by atomic force microscopy. II. Structure-transport properties behavior

This second part of our research on the morphology of the polyurethane-based pervaporation membranes studied by atomic force microscopy (AFM) presents analysis of the structural characteristics, reported in the first part of the paper, with regard to transport properties of the polyurethanes determined from sorption experiments. The correlation has been found between the sorption equilibrium values, as well as the diffusivity of the permeating solvent, and morphology of the membranes studied. This can be related to the restricting role of the hard segment domains in suppressing the membrane swelling, as well as in making the movement of the permeating molecules more tortuous. AFM was also utilized to trace the morphology alteration expected to take place in the membranes exposed to solvents. The results have shown that this phenomenon can be observed for the polyurethanes with developed micron-sized structures after treating with solvent of a high swelling power. In that case, microstructural transformation from circular structures into more perfectly ordered pseudo-lamellae have been found to occur. The solvent sorption/desorption process was found not to affect the membrane initial morphology.

Surface Morphology of the Polyurethane-Based Pervaporation Membranes Studied by Atomic Force Microscopy. I. Effect of the Polyurethane Molecular Structure

Atomic force microscopy (AFM) was employed to study the surface morphologies of the polyurethane-based pervaporation membranes and to evaluate the effect of the polyurethane (PU) molecular structure. Segmented poly(tetramethylene oxide)-based PUs varying in the length of both segments as well as in the structure of the hard segments were tested. Small spherical or extended hard domains, on the size range of tens of nm, and their large, interconnected associates for a higher hard segment volume fraction, have been observed at relatively flat surface of the diamine-based PUs. The surface of the diol-based PUs appears to be generally much coarser and shows globular or circular structures of a few micron size which are thought to be composed of the hard segment lamellae. The morphology variations observed by AFM were found to correlate well with the small-angle X-ray scattering (SAXS) data revealing the necessity of the periodic arrangement in space of the segmental level domains for the formation of a higher level of the domain morphology.

Reaction of oxetane with K+(18-crown-6)K– complex; a convenient route to one-pot metallation

A novel reaction of K+(18-crown-6)K– complex with oxetane yields the organometallic compound potassium γ-potassiopropoxide, a very efficient new metallating agent and a useful reagent in chemical synthesis.

TEMPERATURE EFFECTED STRUCTURAL TRANSITIONS IN POLYURETHANES SATURATED WITH SOLVENTS STUDIED BY SAXS SYNCHROTRON METHOD

ABSTRACT A set of segmented polyurethanes (PU) differing in the hard-segment structure was saturated with solvents and after the equilibrium saturation was reached, put to temperature-dependent SAXS investigations. The time-resolved mode of SAXS measurements with a linear increase of temperature from −70°C to +70°C, i.e., within the temperature range between Tg of soft and hard segments, was applied. The order-order transition leading to a greater degree of order was found at higher temperatures for almost all systems investigated. Some of the PUs exhibit two kinds of microphase separated domains. The results obtained are discussed with respect to the mean-field theory of copolymers and Koberstein and Stein model for hard microdomain structure in PUs, and correlated with temperature dependence of membrane permeability in pervaporation process.

Characteristics of horizontal macroturbulence due to the currents in the Baltic Sea

On the basis of current measurements in a number of sites in the southeastern and central Baltic, the following parameters of horizontal turbulence were estimated: components of turbulence intensity, moments of the correlation matrix, horizontal eddy-viscosity coefficients and directions of the extreme exchange in the horizontal plane. The exchange coefficients were calculated by the Ertel method. Exemplary empirical probability distribution (histograms) of the pulsations of current velocity components and the power spectra were shown. Changes in the turbulence parameters, depending upon the temporal scale the measure of which was assumed to be the averaging period of a cosine filter, were analysed. The influence of inertial oscillations upon the magnitudes of horizontal turbulence characteristics was shown.

Sorption Behavior of Permeants in the Polyurethane‐Based Pervaporation Membranes Studied by DSC

Differential scanning calorimetry (DSC) was used to study sorption behavior of various liquid permeants in the pervaporation membranes formed of homologous series of polyether‐, polyester‐, and polydiene‐based polyurethane elastomers. It has been found that there are three major types of liquid permeant within the membrane: (1) non‐crystallizable liquid, (2) crystallizable‐bound liquid, and (3) crystallizable‐bulk liquid. The kind and number of these forms and their relative contribution appear to be a characteristic feature of a particular system and depend on the specific interactions between permeant and membrane material and between permeant molecules themselves. For weak polymer‐permeant interactions compared to those concerning permeant, crystallizable‐bulk liquid (3) has only been detected within the membrane. For moderate polymer/permeant interactions, represented by the sorption equilibrium values falling around 30%, the permeant in two different forms, (1) and (3), of various composition has been found to exist. For strong polymer/permeant interactions, all types of permeant have been observed including a form (2) classified as crystallizable‐bound liquid. This type of liquid permeant, showing complex melting endotherm of significantly depressed Tm values, has been identified for the first time for permeants without hydrogen‐bonding ability. The observed phenomena are considered as general behavior of membranes under pervaporation conditions and are expected to have an effect upon permeation.