T. T. Todosiichuk

Selective adsorption from melts of polymer blends

Abstract Specific features of molecular mobility were studied by NMR in melts of polyethylene, poly(butyl methacrylate) and their blends in dependence on the content of individual polymers and on the concentration of a filler. The fraction of immobilized segments has been determined for both polymers. In melts of PE-PBMA blends it is the latter polymer which is preferentially sorbed on the surface of the filler. Composition and thickness of the boundary layer have been determined.

Features of molecular mobility manifestations of adsorbed chains in adsorption from solutions of polymer mixtures under conditions of adsorption equilibrium

Abstract By the NMR method, the molecular mobility was investigated of polystyrene and poly(butyl methacrylate), adsorbed from their individual solutions and from their mixtures in a common solvent under conditions of adsorption equilibrium, in dependence on the polymer concentration, content of adsorbent and temperature. The fraction of the hindered monomer units was determined, characterizing their binding by the surface and the hindrance of the molecular motions of a sequence of monomer units due to adsorption of the end unit on the surface. It was shown that the molecular mobility of the adsorbed molecules substantially depends on whether the macromolecules are adsorbed as isolated coils or as aggregates.

Study of adsorption of polymer mixtures from solutions in a common solvent on a solid surface

The authors have studied the adsorption and determined the fraction of bound segments P in the systems polybutyl methacrylate-butadiene-nitrile rubber-Aerosil and polybutyl methacrylate-polystyrene-Aerosil. The isotherms were obtained with extremes the position of which on the adsorption isotherms depends on the nature of the polymer and concentration of the solution. The value p changes within wide limits with the concentration of the solution from which the adsorption layer is formed. The mutual influence of the polymers studied on adsorption from the mixtures was found. It was established that the nitrile rubbers from mixtures with polybutyl methacrylate are not adsorbed although they have an important influence on the adsorption of polybutyl methacrylate and the value p. It is shown that for a different adsorbent-solution ratio the values of p and the form of the isotherms significantly change both for the individual solutions of the polymers and their mixtures. The results are explained in terms of the molecular-aggregative mechanism of adsorption.

Polyurethane (PU) elastomers based on α,ω-oligobutadiene nitrile diols☆

Abstract The properties of polyurethanes (PU) based on oligoisoprene diols were investigated in earlier work [1]. This had shown that the replacement of the oligoether by the oligodiene block in the PU chain changed the structure of the network and the physico-chemical properties of the material. The contribution made by physical bonds to the overall network density in oligodiene-based PU was found to be smaller than that in oligoether-based ones. The intermolecular reaction energy characterized by the intensity of the cohesion places the PU in a position between the normal PU and natural rubbers. The examination of PU based on dienes of a different nature, i.e. containing functional groups capable of forming physical bonds, was therefore thought to be worthwhile. This communication describes the study of urethane elastomers based on oligobutadiene nitrile diols containing nitrile groups, and produced by free-radical polymerization [2]. We believe the introduction of the polar nitrile groups into the oligodiene molecule to change some of the elastomer properties, which had been produced previously, because of the possible reinforcement of molecular interaction. This is in some way analogous to the change of urethane elastomer properties due to the exchange of the ether for an ester block with a C=O group, which is able to form additional physical bonds with other polar groups; this will affect the ultimate properties of the polymers based on them.

Nanostructure of polymer layers formed upon the adsorption from binary and ternary solutions

Thicknesses of nanolayers formed upon the adsorption from dilute and semidilute solutions of polystyrene, poly(butyl methacrylate), and their mixtures on the surface of solid SiO2 are estimated on the basis of adsorption isotherms and atomic force microscopy measurements. It is established that the thickness of an adsorption layer is determined by the sizes of individual macromolecular coils and clusters arising in a solution. In the case of polymer blends, adsorption leads to the formation of mosaic structures with the alternation of polymeric components in the substrate plane; the characteristic size of a domain is ≈200 nm for each component. It is shown that adsorption layers formed on the surface of a silicon single crystal (covered with intact oxide) are fractal objects whose dimension depends on the nature of polymer and conditions of its adsorption.

Adsorption of polymer mixtures from dilute and semidilute solutions

Abstract The adsorption of mixtures of incompatible polymers (polystyrene and polydimethyl siloxane) from solutions in a common solvent (ethyl acetate) in the cross-over region is studied. Adsorption isotherms from particular solutions and their mixtures in the concentration range before and after the critical concentration for overlapping of the polymer coils are given. To explain the isotherms obtained, thermodynamic polymer-solvent interaction parameters, the unperturbed dimensions of the macromolecules in the given solvent, and the dimensions of the polymer aggregates are determined as a function of the concentration of the solution. It is shown that the maximum aggregation is observed in the region before the critical concentration. On attaining critical concentrations the degree of aggregation is sharply decreased because of compression of the polymer coils.

Investigation of the thickness of adsorbed oligomer layers on solid surfaces

Abstract Rheological investigation of epoxide oligomers and their solutions in DMFA filled with glass powder has shown that, in such systems, a spatial fluctuation network is formed. From the results of viscometric investigations, the thickness of the epoxide layer adsorbed on the glass powder in the transfer of oligomer molecules from the oligomer phase to the solid surface in the absence of the solvent has been calculated. On the basis of structure-formation data and the fact that the thickness of the adsorbed layers is independent of concentration and temperature, conclusions have been drawn concerning the migration of aggregates of oligomer molecules during their adsorption on to the solid surface, the special features of the flexibility of the oligomers being taken into account.

Nanocomposites based on silicon dioxide. Preparation and properties

The literature devoted to the preparation of nanocomposites based on polyurethane and epoxy polymers and silicon dioxide is reviewed. The main methods for their production are summarized, and the properties of resulting materials are presented. The synthesis, properties, and structure of the polymers obtained by the sol-gel technique are described in detail.

Structural changes in blends of linear polymers during their physical aging

Structural transformations in the blends of linear polymers polyurethane and polystyrene during multistage physical aging are studied. Effects of the temperature and time of heat treatment and the rate of cooling after heat treatment on the dynamic mechanical properties of the blends are analyzed. Aging at T = 110°C is accompanied by noticeable structural transformations in the polyurethane phase, while chemical changes are absent, as evidenced by thermogravimetric analysis and IR spectroscopy. Additional physical bonds and topological entanglements presumably form between chains in the blends of linear polymers during physical aging.

Effect of fire retardants on fire-resistance and adhesion properties of epoxy urethane compositions

The results of investigating the effects of various fire retardants on the fire-resistance of epoxy urethane compositions are presented. It is shown that the simultaneous presence of phosphorus and bromine, as well as oxides and hydroxides, favors efficient coke formation and a reduction in combustibility while retaining the physicomechanical characteristics of an epoxy urethane adhesive.