Yu.P. Gomza

Microphase structure features of network block polymer over a wide temperature range

Abstract Changes in the microheterogeneous structure of a network block polymer based on diene and epoxy blocks have been studied using the small-angle X-ray scattering technique with a position sensitive detector. The formation of a three-dimensional chemical bond network is shown to result in microphase separation of chemically distinct blocks. The resulting microphase structure is stabilized by the three-dimensional network which prevents the establishment of a thermodynamic equilibrium in the system over a wide temperature range.

The influence of the size and degree orderdering of macro-rings on the synthesis of polyrotaxanes☆

Polyrotaxanes have been synthesized by the radical polymerization of styrene in the presence of a cyclic urethane (CU) derived from triethylene glycol and hexamethylene diisocyanate (CU-B) (Statistical method) and by styrene polymerization in presence of ordered “swarm” complexes of CU-B and ZnCl2. A mechanism of polyrotaxane formation has been proposed, involving the preliminary swelling of the macro-rings in the monomer. The structure of these compounds was investigated by NMR and X-ray spectroscopy. The number of monomer units in one ring was calculated. A comparison of results obtained with analogous data on polyrotaxane synthesis based on a smaller ring of this homologous series (the CU from diethylene glycol and hexamethylene diisocyanate), permitted an elucidation of the effect of ring size and “swarm” complex dimensions on the degree of “piercing” of the rings by a polymer chain. The mechanisms obtained were explained with the aid of data on formation of complexes of both CUs with ZnCl2 and the results of studying molecular models of these rings and the polyrotaxanes based on them.

Study of the structure of porous polyethylene by variation in contrast

Abstract Wide and small angle X-ray scatter in the systems porous polyethylene-low molecular weight liquid has been used to investigate the features of supramolecular organization of the matrix of porous polyethylene and establish the character of the micropores. The peculiarity of the microporous samples consisting in the presence of thin layers and lamellae of polymeric material between pores filled with low molecular weight liquid results in the penetration of its molecules into the amorphous regions of structure even in the case of liquids comparatively inert in relation to polyethylene such as piperidine, dimethylformamide and dibutyl phthalate.

Morphological evaluation of changes in the supercrystallite structure of two component polymer mixture obtained from melt

Abstract An investigating the morphology of incompatible polymer mixtures it was shown that the homogeneity of supermolecular structures observed using the electron microscope, is not evidence of compatibility on a supermolecular level, but is merely the result of a weak optical contrast. Individual morphological structures can be detected in these systems by transfer to the oriented state. Separation into two clearly expressed phases in this case distinctly indicates the absence of compatible supermolecular structures. When an intermediate layer is formed at the interface, this is a typical sign of morphologically incompatible polymers.

Porous structure of cellulose acetate ultrafiltration membranes of various degrees of saponification

Abstract The porous structure of ultrafiltration cellulose acetate membranes and the effect of alkaline saponification on their structure are studied by small-angle X-ray analysis and by sorption of the vapours of an inert sorbate. It is shown that these membranes have a two-level porous structure. Saponification is accompanied by a decrease in the membrane pore size, which is a result of an increase in the number of physical “cross-links” of the three-dimensional gel network.

Structure of a polycarbonate-binary fire-retardant composition system and its pyrolysis products☆

Abstract The structure of a polymer composition of decreased combustibility, based on polycarbonate and a fire-retardant system containing phosphorus and vanadium, and also the structure of pyrolysis residues from this composition are studied by wide-angle X-ray diffraction analysis and electron microscopy. Modification of the polycarbonate results in insignificant changes in the character of the supermolecular structure, but the structure of the pyrolysis residues is thus significantly changed. The microporosity of the modified and unmodified materials also differ markedly. The fine structure of the pyrolysis residues of the modified polymer retains the characteristic elements of short range order of the original polymer. The presence of a fire-retardant system results in the formation of pyrolysis residues in the form of a three-dimensional framework of cell dimensions up to about 100 μm.

Kinetics of disappearance of structural homogeneity in the system poly(vinylidene fluoride)-poly(methyl methacrylate) induced by crystallization of poly(vinylidene fluoride)☆

Abstract The structure of blends PMMA-PVF 2 has been investigated by wide-angle X-ray diffraction and small-angle X-ray scattering as well as by electron microscopy in dependence on the regime of thermal treatment. Phase separation crystal-liquid in a 1:1 homogeneous mixture (obtained by quenching of melt) proceeds according to the nucleation mechanism and is diffusion-controlled. In the last stages of phase separation a coalescence of the growing nuclei is observed.

Antifriction and Construction Materials Based on Modified Phenol-Formaldehyde Resins Reinforced with Mineral and Synthetic Fibrous Fillers

Novel polymer composite materials (PCM) based on resole phenol-formaldehyde resins modified with polyamide and reinforced with a combination of organic and inorganic fibrous fillers have been developed. PCM are characterized by a Charpy impact strength of up to 250 kJ/m2, an ultimate strength in static bending of up to 468 MPa, an ultimate strength in compression of up to 178 MPa, a Martens thermal stability of up to 300 °C, a friction coefficient of up to 0.12, and mass wear of up to 0.76 mg/(cm2 · km). They can be used for the fabrication of products intended for antifriction and constructional purposes.

Effect of conditions of treating linear polyethylene on the character of the microporous structure formed

Abstract The character of the microporous structure of systems based on linear polyethylene, obtained by successive high temperature treatment in m -xylene and DMFA with subsequent crystallization of the system at room temperature is studied by small-angle X-ray scattering. It is shown that by varying the time the gel is in DMFA at 138°C it is possible to obtain a purposeful change in the nature of the highly dispersed microporous structure formed, in the ratio of the open and closed pores, and also in their particle size distribution.

The Interrelation Between the Microphase Structure of Sequential Interpenetrating Polymer Networks and the Crosslinking Density of Penetrating Networks

Abstract The microphase structure of single polyurethane (PU) and acrylate networks as well as sequential interpenetrating polymer networks (IPNs), produced by the forming of a PU network in the presence of monomers of a penetrating network, was studied by small- and wide-angle x-ray analysis. It was established that each network component was of a two-phase structure consisting of disordered phase-separated microregions. the higher crosslink density of the acrylate network results in its higher heterogeneity. in IPNs, phase separation of a complex nature is realized: the PU matrix preserves some features of a single network structure, and the second component forms microregions 5-10 nm in size while retaining a certain level of interpenetra-tion of both network components. the microphase structure parameters of such systems are greatly dependent on the crosslink density of the penetrating network. This suggests the influence of a three-dimensional network of chemical bonds on the interdiffusion of branch...