V. I. Shtompel

Phase morphology and molecular dynamics of a polyurethane ionomer reinforced with a liquid crystalline filler

Solution-blended binary composites of ionic segmented polyurethane (SPU-I) and liquid crystalline oligomer (LCO) were characterized by wide-angle (WAXS) and small-angle (SAXS) X-ray scattering, differential scanning calorimetry (DSC), thermally stimulated depolarization currents (TSDC) and dielectric relaxation spectroscopy (DRS). Both components mutually influenced their states of aggregation in blends (most significantly, promoting smearingout of interfaces between stiff and soft chain fragments of SPU-I into broad interfacial regions of intermediate composition). Apparently, the blend with w ¼ 0:10 happened to be most favorable for crystallization of the LCO, while the degree of microphase separation for SPU-I became lower and the distribution of stiff domains by sizes became broader, the higher the LCO content. The overall molecular mobility of SPU-I in blends was significantly reduced. This reduction included the intensity of the secondary and the primary relaxations, and of the interfacial Maxwell–Wagner– Sillars (MWS) relaxation, whereas the transition temperatures remained essentially composition-invariant. The Arrhenius-like behavior for the dc conductivity concomitant to the non-Arrhenius (i.e., Vogel–Tammann–Fulcher) frequency dependence for the a relaxation in blends suggested a decoupling of conductivity from the motion of the SPU-I soft chain segments. � 2003 Elsevier Ltd. All rights reserved.

DC field effect on the structuring and thermomechanical and electric properties of nanocomposites formed from pectin—Cu2+—polyethyleneimine ternary polyelectrolyte—metal complexes

With the use of combined structural methods, thermomechanical analysis, and dielectric spectroscopy, the effect of a dc field on the structuring and properties of ternary polyelectrolyte—metal complexes prepared from a stoichiometric polyelectrolyte complex based on the weak polyelectrolytes pectin and polyethyleneimine and CuSO4 salt, as well as nanocomposites formed from these complexes, has been studied. It has been found that the chemical reduction of Cu2+ cations in the bulk of a ternary complex under the action of a dc field occurs via the formation of a nanocomposite consisting of a polyelectrolyte complex and nanoparticles of only the metal Cu phase, whereas nanocomposite with Cu/Cu2O nanoparticles is formed in the absence of field. With the use of thermomechanical analysis and dielectric spectroscopy, it has been shown that, under a dc field, nanocomposites with higher structural glass-transition temperatures and electric conductivities are formed.

X-ray Study of Structural Formation and Thermomechanical Properties of Silver-Containing Polymer Nanocomposites

The structural organization and thermomechanical properties of nanocomposites prepared from interpolyelectrolyte–metal complex (IMC) involving anionic polyelectrolyte, pectin and AgNO3, and cationic polyelectrolyte, poly(4-vinylpyridine), have been investigated using the methods of wide- and small-angle X-ray scattering and thermomechanical analysis. It is established that chemical reduction of Ag+ ions in the IMC by sodium borohydride results in formation of the nanocomposite based on the “pectin–poly(4-vinylpyridine)” interpolyelectrolyte complex (IPEC) and Ag0 nanoparticles as well. At the same time, the level of nanocomposites’ structural heterogeneity is substantially enhancing, while effective size of the heterogeneity regions decreases. The nanocomposites IPEC–Ag0 prepared are shown much bigger Tg value and enhanced ability for deformation than those for IMC.

Study and characterization of polyurethane composites filled with polysaccharides

Composites based on a segmented polyurethane and polysaccharides (starch, dextrin, and chitosan) have been prepared, and their biodegradation ability has been studied. With the use of pyrolysis mass-spectrometry, SAXS, and WAXS, the structure and chemical composition of the composites before and after their exposure in soil have been characterized. It has been demonstrated that the incorporation of up to 25 wt % chitosan into the segmented polyurethane leads to its structural and chemical modification and makes it possible to increase its strength characteristics and to simultaneously improve its biodegradability. The optimal biodegradability is attained when 15 and 25 wt % starch are introduced into the polyurethane, whereas the use of dextrin for this purpose turns out to be inefficient.

Constant Electric and Magnetic Fields Effect on the Structuring and Thermomechanical and Thermophysical Properties of Nanocomposites Formed from Pectin–Cu 2+–Polyethyleneimine Interpolyelectrolyte–Metal Complexes

Applying wide-angle X-ray scattering method, thermomechanical analysis, and differential scanning calorimetry, the structural organization and properties of nanocomposites formed by chemical reduction of Сu2+ cations in the interpolyelectrolyte–metal complex (pectin–Cu2+–polyethyleneimine) under the influence of a constant magnetic and electric fields have been studied. It has been found that the chemical reduction of Cu2+ cations in the interpolyelectrolyte–metal complex bulk under constant electric and magnetic fields leads to formation of nanocomposite consisting of interpolyelectrolyte complex, including pectin–polyethyleneimine and nanoparticles of the metal Cu phase, whereas nanocomposite with Cu/Cu2O nanoparticles is formed in original state (without any field). It was observed that, under constant field, nanocomposites obtained have higher structural glass-transition temperatures and thermal stability.

Polyurethanes based on asymmetric dimethylhydrazine: Synthesis, structure, and properties

New polyurethanes have been synthesized from asymmetric dimethylhydrazine at a nonstoichiometric ratio of the starting reagents. With the use of various methods, the number-average molecular mass of the polymers has been estimated and conclusions concerning their possible structure have been made.

Comparative study of the structure and properties of ionomeric polyurethane semicarbazides

Abstract Scanning calorimetry, small angle X-ray scatter and stress relaxation have been employed to investigate the ionomeric polyurethane semicarbazides present in the acid or salt forms. Conversion to the salt form of an anion-active polyurethane semicarbazide leads to partial suppression of the capacity of the segments for microphase layering.

The role of the method of synthesis in formation of the structure and properties of segmented polyurethane ionomers

Abstract The influence of the method of synthesis on the structure and properties of cation-active polyurethane semicarbazides has been studied. It was shown that in polyurethane ionomers, prepared by a single stage method, the character and nature of structural heterogeneity is different from that of segment polyurethanes. In polyurethane ionomers, prepared by 2- and 3-stage methods, the structural heterogeneity is the result of segregation of rigid blocks owing to the dipole-dipole and ion-dipole interactions.

Structure and physico-mechanical properties of interfilled oligomer-oligomer compositions☆

Abstract The effect of structure-formation on physical and mechanical properties of compositions obtained by mixing oligoether and oligoester melts was studied by X-ray diffraction analysis, scanning calorimetry and thermomechanical method. Physical and mechanical properties change to a maximum extent when introducing small additives of one component into another. In the range of average compositions of components differences in the phase-aggregate state of oligo-oxytetramethylene glycol and oligobutyleneglycoladipate do not assist in changing the properties of compositions indicated. It was indicated that there are two mechanisms showing the effect of small additives on the structure and properties of oligomer-compositions.

Structure, Morphology, and Properties of Copper-Containing Polymer Nanocomposites

The morphology, structural organization, and thermomechanical and antimicrobial properties of nanocomposites prepared involving a natural and synthetic polymers – pectin, polyethyleneimine, and Cu/Cu2O or Cu nanoparticles – obtained by the chemical and thermal reduction of copper ions in the interpolyelectrolyte–metal complexes have been investigated. Such type of nanocomposites with Cu/Cu2O core–shell nanoparticles incorporated into polymer matrix is obtained due to the chemical reduction of Cu2+ ions by NaBH4 in the interpolyelectrolyte complex, and appearance of the copper’s metallic phase is observed in full extent while BH4−: Cu2+molar ratio being equal to 6.0. Applying thermomechanical analysis, it was observed that transformation of interpolyelectrolyte–metal complexes into nanocomposites results in decreasing of their glass-transition temperature. It is defined that Cu2+ ions thermal reduction in interpolyelectrolyte–metal complexes bulk (while films are heated to the optimal temperature around 170 °С) results in nanocomposites based on interpolyelectrolyte complexes “pectin–polyethyleneimine” and Cu nanoparticles being formed. It has been shown by thermomechanical analysis that the optimal time for complete thermal reduction of Cu2+ ions to metallic copper at T = 170 °С is 30 min. The antimicrobial investigations of the elaborated nanocomposites revealed they possess a high antimicrobial activity against S. aureus and E. coli strains.