The rheological properties of a liquid containing two types of basic centers and hydroxyl groups (BGE-Im), as well as protic ionic liquids (ILs) derived from it, were studied in a wide range of shear rates ( (center dot) gamma ) (10 - 6 - 10 3 s -1 ) at various temperatures from 10 to 50 degrees C. Viscosity ( I ) of the BGE-Im does not depend on the scanning direction of shear stress ( Cr ), i.e. this compound behaves like a Newtonian fluid over the entire range of Cr . The dependence log I (1/T) of BGE-Im in Arrhenius coordinates is linear. Protonation of basic centers of BGE-Im leads to a strong increase in the viscosity of ILs obtained on its basis, and the temperature dependence of the viscosity of these ILs is described by the Vogel - Fulcher - Tammann (VFT) equation. It has been established that in the region of low shear rates, the viscosity of the ILs increases with decreasing shear rate, which leads to the appearance of a yield stress ( Cr Y ). This indicates the formation of a fluctuation rheopectic structure in the ILs. In this sense, ILs are heterogeneous systems and their behavior is similar to that of highly concentrated suspensions and emulsions. For the first time, a quantitative comparison between the parameters of the VFT equation, the fragility (according to Angell ' s model) of ILs, the relative coordination number of ILs molecules and the rheological yield stress characterizing the shear-induced fluctuation rheopectic structure of ILs has been made and the relationship between these characteristics has been shown.

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 non-ionic 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.

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–crosslinked 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.

The scaling approach was used to the interpretation of the rheokinetics of poly(methyl methacrylate) and crosslinked polyurethane formation as well as of its in situ forming blend. It was shown that such approach makes it possible to characterize more completely the processes of phase state change of the system that can not be detected by the traditional methods of describing the experimental rheokinetic results.

The structure and rheological behavior of a reactive oligomeric ionic liquid (OIL) have been studied. The OIL has a linear structure and contains ionic fragments of two types at both ends of oligo(ethylene oxide) chain. The ionic fragments are represented by secondary amino groups and nitrogen-containing heterocycles protonated with ethane sulfonic acid. The results obtained using rotational rheometry in different dynamic regimes indicate that, in the linear region of deformation at temperatures T < 20°C, this OIL exhibits the behavior of an elastic solidlike body. The components of the complex shear modulus (G ' ~ 107 Pa and G '' ~ 106 Pa) are independent of frequency ω and temperature. At the same time, its complex dynamic viscosity is independent of temperature and decreases with an increase in ω (in logarithmic coordinates, the dependence is linear and has a slope close to unity, which is a formal sign of the existence of a yield stress). At T ≤ 20°C in the nonlinear region of periodic deformation, a crossover is observed in the amplitude dependences of G ' and G '', which indicates that the critical shear stress is reached. As a result, the OIL passes into the liquid state (G '' > G '). The boundary, which is located at nearly 30°C, is characterized by equality between G ' and G '' in a wide range of strain amplitudes. The structural transformations induced by thermal and mechanical energies have been explained using a hypothesis of the existence of micellar structures and a “normal micelle–reverse micelle” transition in the OIL, as well as changes in micelle shapes. The analysis of the temperature dependences for the viscoelastic characteristics and scattered light intensity, as well as the data of DSC and optical microscopy, has led to the hypothesis that at, T = 21–28°C, the OIL may occur in an ordered state similar to the liquid-crystalline one.

The relationship between the rheokinetics of the in situ formation of a linear poly(methyl methacrylate)–crosslinked polyurethane blend in the presence of various amounts of an oligomeric azo initiator containing polyurethane chain fragments and groups able to initiate the radical polymerization of methyl methacrylate and the process of phase separation, the morphology, and the mechanical properties of the final products is studied. It is shown that the times of phase separation and gelation are interrelated and depend on the concentration of the azo initiator in a simple manner. This initiator affects the structural and rheological transitions in the system and leads to the formation of morphologies with smaller domains. The most stable system with the best dispersion of polyurethane in poly(methyl methacrylate) is the blend containing 0.002 mol/L azo initiator that possesses the optimum mechanical properties.

Изучена связь реокинетики формирования in situ смеси линейный полиметилметакрилат–сшитый полиуретан в присутствии разного количества олигомерного азоинициатора, содержащего фрагменты полиуретановой цепи и группы, способные инициировать радикальную полимеризацию метилметакрилата, с процессом фазового разделения, морфологией и механическими свойствами конечных продуктов. Установлено, что время фазового разделения и гелеобразования взаимосвязаны и находятся в простой зависимости от концентрации азоинициатора. Такой инициатор влияет на структурно-реологические переходы в системе и приводит к образованию морфологии с более мелкими доменами. Наиболее стабильной системой с лучшим диспергированием полиуретана в полиметилметакрилате является смесь, содержащая 0.002 моль/л азоинициатора, которая обладает оптимальными механическими свойствами.

The viscosity of oligoisoprenes obtained by radical polymerization in alcohol solutions with hydrogen peroxide as initiator has been measured at various temperatures and rates of shear. It was established that the invariant dependency of shear stress and viscosity do not depend on molecular weights and functionalities. The identity of oligoisoprenes appears in the activation energy that shows a changeable tendency. This behavior could be explained by a change of the mechanism of viscous flow.

The rheological properties and morphology of flow during the in situ formation of linear polyurethane and poly(methyl methacrylate) blends of various compositions are studied. At a certain conversion of the components, the initial homogeneous blend undergoes phase separation, as evidenced by the nonadditive dependence of the logarithm of viscosity on blend composition. For individual components, the gel points correspond to appreciably different conversions. For components in blends of various compositions, this difference is less pronounced and associated with the kinetic conditions of blend formation. The morphology of flow of the reaction blend over the time (or conversion) between the onset of phase separation and gelation during flow with a high shear rate is determined by the blend composition and the ratio between the viscosity of the dispersion phase and the matrix.

The viscoelastic characteristics of the blends of poly(methyl methacrylate)/poly(styrene- co -acrylonitrile) (PMMA/SAN) were investigated at various temperatures below, near, and above the phase separation temperature. The investigated polymer system is characterized by a lower critical solution temperature. Rheological behavior of the blends in the region of a phase separation was compared with change of the light scattering intensity. The presence of nanofillers in the blend results in that the phase separation occurs at a higher temperature. At the isothermal conditions, the phase separation begins earlier and proceeds with a higher rate as compared with the same blend without filler. The results of the study show the considerable change of the viscoelastic characteristics of PMMA/SAN when the polymer system passes from the homogeneous state to the heterogeneous one. Such characteristics as the dependence of the storage modulus ( G ′ ) on the loss modulus ( G ″ ), the dependence of the loss viscosity ( η ″ ) on the dynamic viscosity ( η ′ ), the dependences of the complex viscosity ( η *), and the free volume fraction ( f ) on the blend composition are the most sensitive to the phase separation. The phase separation affects the characteristics G ′ ( ω ), where ω is the frequency only in a low-frequency range. Temperatures of phase separation were estimated using dependence G ′ ( T ) at ω , which is the constant in the range of low frequencies.

Blends of an ethylene/vinyl acetate copolymer (EVA) and polyisobutylene of various compositions were prepared by mechanical mixing at a temperature above the melting point of EVA (T-m(EVA)) but below the upper critical solution temperature of 170 degrees C for given blends. The rheological properties of the components and blends were studied in the region of small-amplitude oscillating deformation at temperatures above and below T-m(EVA) in the frequency range of 0.01-100 rad/s. At temperatures lower than T-m(EVA) the rheological properties were deter mined by the existence of the yield stress. With diminishing frequency, the viscosity increased, and the plateau in the relaxation spectrum at low frequencies broadened. The morphology of the blends depended on the conditions of sample heating. The introduction of a finely dispersed filler into the blends led to an anomalous drop in the viscosity. The morphology of the systems that arose by mechanical blending of the molten components was the important factor in the rheological behavior. The observed effects were examined in the framework of the concept of structural networks formed in melts by nonmelted crystallites of EVA. (c) 2006 Wiley Periodicals, Inc.