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The work is devoted to the study of self-organization processes in disperse systems. The most relevant aspect of such self-organization is the relationship between structure and properties in polymer composites. In this paper, we are talking about dispersion media (matrices), namely, the mechanisms of phenomena and interactions that occur during the deformation of disperse systems. These interactions depend on the properties and processes of self-organization of dispersion media and determine the properties of future polymer composites. One of the most popular dispersion media are diene oligomers (liquid rubbers). In this work, the rheology of diene oligomers with terminal hydroxyl groups (HRD) was studied in a wide range of shear rates and temperatures. It was assumed that in the case of oligoisoprene, an increase in the activation energy of viscous flow (from 46 to 95 kJ/mol) with decreasing temperature is associated with an increase in the density of the fluctuation dynamic structure with an increase in the volume content of associates of polar OH groups (i.e., nonionic micelles) with a decrease in thermal energy kT (k is the Boltzmann constant). The results of rheological studies for the first time (for nonionic liquids) were presented within the framework of the Angell's concept, from which it followed that these systems are fragile, i.e. they are very promising in terms of studying structure formation in a shear field. [ABSTRACT FROM AUTHOR]

Based on the experimental data on the rheology of dispersions of hydrophobic aerosil (Am) in a low molecular weight hydrocarbon medium, the possibility of using a «micellar» mechanism for the formation of a bulk structure for such dispersions is considered. A model of such a structure before, during and after shear deformation is proposed, which makes it possible to interpret experimental data on the rheology of dispersed systems. The results of the study of rheokinetics are presented in a new visio -- from the point of view of self-organization under the influence of the shear field. The PMMA--PU--Am system was considered as a polymer composite (PC), in which the matrix is the poly(methyl methacrylate) (PMMA) being modified, and the dispersed phase is a mixture of polyurethane (PU) with Am. It has been shown that during the reaction formation of this composition, the conditions of shear deformation of the system correspond to those at which self-organization and fixation of the coagulation rheopex structure of the nanofiller in PC is possible at the moment of reaching very high viscosity values (gel-point), when diffusion processes will be practically frozen. Two concentration regions of Am were predicted (before and after the percolation threshold), where an enhancement of the mechanical characteristics of PMMA can be expected. The relationship between the rheokinetics of the formation of a linear PMMA--cross-linked PU mixture in the presence of different amounts of oligomeric azo-initiator containing fragments of the polyurethane chain and groups capable of initiating radical polymerization of methyl methacrylate and the process of phase separation, morphology and mechanical properties of the final products has been established. It was shown that the time of phase separation and gelation are interrelated and there is in a simple dependence on the concentration of the azo-initiator. Such an initiator affects the structural-rheological transitions in the system and leads to the formation of morphology with smaller domains. The most stable system with the best dispersion of polyurethane in polymethyl methacrylate is a mixture containing 0.002 mol/L of azo-initiator, which has improved mechanical properties and increased impact viscosity. [ABSTRACT FROM AUTHOR]

Nanoparticles (mean size about 7 nm) of the standard pyrogenic Aerosil 1380 (Degussa) pregrafted by γ-irradiation with styrene were melt-compounded with the general purpose isotactic polypropylene homopolymer to prepare four nanocomposites with filler volume contents up to 4.68%. Storage G′(ω) and loss G″(ω) shear moduli in the melt state (measured in the range of linear viscoelasticity at three temperatures in the frequency window spanning about three decades) were treated to derive the relaxation times spectra h(Τ) using the NLREG computer program based on Tikhonov's method of non-linear regularization. The experimental data were interpreted in terms of the tentative model highlighting the structural significance of the ratio of mean thickness of polymer interlayer between neighboring filler particles, L, to the mean radius of gyration of a polymer coil, Rg. In the range of very low filler loadings characterized by large scaled distances, L/Rg≥1, all nanocomposites behaved as Newtonian liquids in which the self-diffusion of macromolecular coils was, however, slowed down. The onset of plastic yield phenomenon for a nanocomposite with the filler volume content as low as 4.68% was regarded as the experimental evidence for the shear-resistant, infinite cluster of filler particles coated with polymer boundary interphase when the scaled distance approached the 'critical' value, L/Rg≤1. [ABSTRACT FROM AUTHOR]

Based on the review of micelle formation, concepts of structure formation in deformable singlecomponent and multicomponent polymer and colloid systems, as well as experimental data on the rheology of dispersions of hydrophobic aerosil (Am) in a low-molecular-weight hydrocarbon medium, the use of a "micellar" mechanism for the formation of a bulk structure is considered. A model of such a structure is proposed before, during and after shear deformation, which allows interpretation of experimental data on the rheology of dispersed systems.It is shown that during the reaction formation of the PMMA -- PU -- Am composition, the conditions of shear deformation of the system correspond to those for which self-organization and fixation of the coagulation rheopexy structure of the nanofiller in the PMMA -- PU binary matrix is possible at the moment it reaches very high viscosity diffusion processes will almost be "frozen". Two concentration regions of aerosil Am are predicted (before and after the percolation threshold), where we can expect an increase in the mechanical characteristics of the impact-resistant PMMA. [ABSTRACT FROM AUTHOR]

The influence of modified hydrophobic aerosil on the formation, viscoelastic and mechanical properties of interpenetrating polymer networks (IPNs) of poly(methyl methacrylate)/polyurethane has been investigated. It was established that the introduction of a nanofiller directly into the reaction mixture and an increase in its concentration causes the slowdown of both reactions: polymerization and urethane formation. The process of phase separation that accompanies chemical reactions takes place in two stages. The nucleation mechanism is preferred at the first stage; the spinodal mechanism is preferred at the second one. The formation of the phase-separated morphology of the obtained structure is confirmed by the results of optical microscopy: at the nanofiller concentration of 1 % (by weight) interconnected periodic structures are formed, and at the concentration of 7 % (by weight) structures with non-uniform distribution of phases are formed. The established relationship between the values of impact strength and the mechanical loss modulus indicates a possible location of the nanofiller mainly in the interfacial region. It has been shown that IPN with 1 % (by weight) of hydrophobic aerosil has the best value of impact strength. It is assumed that the impact strength for the filled IPNs is determined by the coagulation structures formed by the aerosil nanoparticles. [ABSTRACT FROM AUTHOR]