This work is aimed at developing a kappa-carrageenan (kCR) gel with increased methotrexate (MTX) content. β-Cyclodextrin (βCD), which is able to inclusion complex formation with MTX, has been used to increase the drug concentration in the hydrogel. The rheological behavior of the designed gels was investigated and the influence of MTX and βCD on the viscoelastic properties of kCR gel was studied in detail. The effect of βCD and its concentration on the MTX-releasing rate from the kCR gels was examined. The properties of kappa- and iota-carrageenans loaded with MTX were compared and the differences observed were explained in terms of different binding affinities of MTX to these polymers. The obtained gels provided desirable viscoelastic properties useful for topical application.

We investigate the structure–property relations of the multiblock copolymers of norbornene with cyclododecene synthesized via the macromolecular cross-metathesis reaction between amorphous polynorbornene and semicrystalline polydodecenamer in the presence of the first-generation Grubbs catalyst. By adjusting the reaction time, catalyst amount, and composition of the initial system, we obtain a set of statistical multiblock copolymers that differ in the composition and average length of norbornene and dodecenylene unit sequences. Structural, thermal, and mechanical characterization of the copolymers with NMR, XRD, DSC (including thermal fractionation by successive self-nucleation and annealing), and rotational rheology allows us to relate the reaction conditions to the average length of crystallizable unit sequences, thicknesses of corresponding lamellas, and temperatures of their melting. We demonstrate that isolated dodecenylene units can be incorporated into crystalline lamellas so that even nearly random copolymers should retain crystallinity. Weak high-temperature endotherms observed in the multiblock copolymers of norbornene with cyclododecene and other cycloolefins could indicate that the corresponding systems are microphase-separated in the melt state.

Rheological and morphological properties of heavy crude oil-in-water (O/W) emulsions have been studied. Two series of emulsions were considered: first, the surfactant type remained constant, while the continuous phase content was varied and second, the surfactant type was varied while the continuous phase content remained constant. Under stress-controlled shearing, all samples exhibit viscoplastic behavior. The rheological properties are directly related to the morphology of the emulsions which vary in size of dispersed phase droplets and their inherent structure. Adding a surfactant characterized by a high value of interfacial oil-water tension results in a decrease in the yield stress (which is a measure of the interparticulate structure strength). The same effect is attained by increasing the water content. Meanwhile, these two factors determine the viscosity which can be much lower than that of the basic heavy crude oil if the O/W type of emulsions has been created. Special attention was paid to the viscoelastic properties which have been scarcely reported. Correlations were found between the surfactant properties, composition of the emulsion, and rheological characteristics of emulsions (yield stress, apparent viscosity, and viscoelastic properties), which allows for reduction in the crude oil viscosity down to a low enough level acceptable for pipe transportation.

A series of experiments has been carried out in order to construct a master curve generalizing the combined impact of temperature and low viscosity additives on the viscosity of heavy crude oil. The goal was to establish the temperature-diluent concentration relationship to achieve a defined limit of heavy crude oil viscosity suitable for tube transportation. The ultimate viscosity limit was assumed to be 0.2-0.4 Pa center dot s. Three different industrially acceptable diluents (light oil, light gas oil, and spindle oil) were used for mixing with heavy oil. The viscosities of the mixtures were measured across the whole concentration range at temperatures from -20 to 50 degrees C. The experimental temperature and concentration dependencies of the mixture viscosity were described by corresponding equations. The data enabled to construct master curves for the determination of temperature-concentration relationships for the suitable viscosity level. The proposed approach can be applied to different heavy crude oil-diluent mixtures.

A systematic study of the influence of surfactant and stabilizing polymer additives on the rheological properties of heavy oil was carried out. The aim was to optimize the recipe for the most effective reduction in the oil viscosity. A total of 41 versions of the emulsion were prepared using different protocols. Creation of the emulsions with different recipes and modes of mixing led to a regulation of their morphologies, which determined the rheological properties of the final products. In all cases, emulsification resulted in a transformation of the oil from Newtonian behavior to a viscoplastic medium with a blurred yield stress. Dependent upon the composition, the yield stress was decreased up to 0.6 Pa and the viscosity at high shear obtained a value up to 50 mPa s, which is lower than the viscosity of crude oil by 34 times. The efficiency of the viscosity reduction increased with a decreasing temperature.

Diaminodiphenyl sulfone is used as a curing agent to obtain an epoxy-resin-based binder with improved thermal stability. The kinetics of curing of this composition is studied by rheokinetic and calorimetric methods. It is shown that complete conversion is attained at a temperature of 200°С or higher. The rate of viscosity increase in the course of time in curing under flow conditions does not depend on the shear rate; the viscosity changes monotonically. The curing reaction occurs in the homogeneous mode without separation of a crosslinked polymer; it is described by a second-order equation with self-deceleration at low temperatures. The rheokinetic characteristics and temperature dependences of kinetic parameters of the process are determined.

The phase equilibrium and rheological properties of poly(1-trimethylsilyl-1-propyne) solutions obtained with tantalum catalysts are studied. For three polymers with different molecular masses, phase diagrams are determined in a number of solvents. From these diagrams, the Hansen solubility parameters of poly(1-trimethylsilyl-1-propyne) are calculated by the method proposed in this work. Dilute solutions of poly(1-trimethylsilyl-1-propyne) behave as Newtonian liquids, whereas the viscosity of viscoelastic concentrated systems decreases as the shear rate grows. The molecular and rheological characteristics of studied poly(1-trimethylsilyl-1-propyne) samples are compared with the samples prepared with NbCl5 catalysts. Poly(1-trimethylsilyl-1-propyne) obtained with a catalytic system involving tantalum pentachloride is characterized by high intrinsic viscosity and solution viscosity compared to poly(1-trimethylsilyl-1-propyne) prepared with niobium catalyst. The difference in properties is due to the dissimilar ratios of cis and trans units in the samples.

The combined superimposing influences of the surface area of silica nano-particles and molecular weight of polyethylene oxide matrix on the rheological properties of suspensions have been studied. The parameters of both components varied over a wide range: the surface area of silica from 100 to 390 m2/g, molecular weight of poly(ethylene oxide) from 200 to 2 × 105 Da, and concentration of silica from 1 to 13 vol%. In all cases, silica formed aggregates in suspension with apparent diameters of 50 to 230 nm; the higher values were observed for particles with larger surface area. Low-concentration suspensions in an oligomer matrix showed a slight non-Newtonian behavior; the size of silica particles was a determining parameter. Increasing the silica concentration led to dilatancy at high shear stresses. There was a threshold in the concentration dependence of viscosity, beyond which gelation of suspensions occurred. Depending on the silica concentration and molecular weight of the polymeric matrix, the dispersions behaved more like typical colloidal suspensions in a low molecular weight matrix or viscoelastic polymer melts containing an amount of solid filler. An increase in molecular weight of the polymeric matrix resulted in competition between increase in viscosity, appearance of viscoelasticity, and finally the transition from the gel state of a suspension in viscous medium to an elastic fluid.

The analysis of chemically modified copper phthalocyanines (CuPc) by a diazonium treatment is presented. Various amounts (from 0.5 to 100 wt. %) of the 4-benzenediazonium-carboxylate are used as modifier. The modification involves acetate-ion catalyzed arylation of the CuPc aromatic fragments. As a result, new functional groups are fixed on the phthalocyanine's surface (Gomberg-Bachmann reaction in heterophase conditions). The influence of the initial reactants ratio on the content of grafted functional (-C6H4-COOH) groups in the product is examined and quantified by titrimetry and IR spectroscopy. The content of carboxyl groups in the product varies from 0.03 to 0.20 mol(-COOH)/mol(CuPc). The IR spectrum of carboxylated CuPc shows a band with medium intensity in the region of 1720-1690 cm(-1), which corresponds to the Ar-COOH fragment. Dynamic light scattering of aqueous dispersions of carboxylated CuPcs indicates that the increase in diazonium treatment of the surface leads to the increase of the absolute value of zeta potential (from 25 to 44 mV) and the associates size reduction (from 2950 to 270 nm). It also provides the significant increase in colloidal stability of CuPc aqueous suspensions. The obtained data on the assay amount of grafted carboxyl groups, zeta potential and particle's aggregates size of CuPc demonstrate that the modified product properties are stabilized when using the 1:0.3 molar ratio of initial pigment / aryldiazonium salt (initial amount of modifier is 10 % by weight of CuPc).

Possible variants of the rheological behavior of silica model dispersions have been analyzed. Different types of interaction between the particles and a dispersion medium make it possible to obtain different systems from low-viscosity sols to gels. Proton-donor (water) and aprotic (dimethyl sulfoxide) media have been used for comparison. Dispersions in the aprotic medium behave as non-Newtonian viscous fluids exhibiting shear thinning or shear thickening depending on deformation rate. Aqueous dispersions are viscoelastic and viscoplastic objects that exhibit the shear thickening at stresses higher than the yield stress. The introduction of small amounts of poly(ethylene oxide) into the organic dispersion medium initiates gelation. An increase in the polymer content in the dispersion medium above the concentration corresponding to the formation of a macromolecular network promotes an increase in stiffness and strength of the gels. The rheological behavior of gels is influenced by the polymer molecular mass and its affinity for a solvent.

The current work is based on experimental viscosity and compositional data of about 200 crude oil samples from various parts of Russia and the Norwegian continental shelf. Data analyses were performed to estimate correlations between viscosity and density values as well as concentrations of main components from the crude oils of different origins. It appeared that, in some cases, it is possible to establish a general correlation of viscosity increase along with growing asphaltene, resin, and aromatics contents but also a decrease in viscosity with increasing saturates content. The spread of the data points can be rather wide for the oils of different origins. It was observed that asphaltenes from all of the crude oil samples acted as promoters of the viscosity growth at rather low concentrations, while resins and aromatics effectively increased viscosity in a higher concentration range. The effect of asphaltenes on the viscosity of real crude oils seems to be more important than when dissolved in a model solvent (xylene). This means that either the asphaltenes have a different solvation state in crude oils compared to xylene or asphaltenes are not solely responsible for the high viscosity of the crude oils.

A comparative study of the rheological properties for typical heavy and light crude oils of Russian origin and their mixtures was carried out. The chemical composition of both species was characterized by liquid chromatography and gas chromatography mass spectrometry. The light oil is a viscoelastic non Newtonian fluid due to the presence of paraffin waxes; their concentration and the melt temperature were determined by the DSC method. The presence of crystallizable waxes provides viscoelasticity and the appearance of yield stress. Above 28 degrees C, the light oil transforms to a non-elastic Newtonian fluid. The heavy oil demonstrates Newtonian behavior even when cooled to -30 degrees C. However, the heavy oil becomes viscoelastic at temperatures below 0 degrees C, which does not indicate waxes, but rather the presence of high molecular-weight components. The temperature dependence of the viscosity of the heavy oil is well fitted by the WLF equation. The viscosity of the heavy oil is higher than the light oil above the melt temperature of paraffin waxes and vice versa. In the heavy-light oil mixtures, the melt temperature decreases and the yield stress diminishes due to the decrease in wax content. At the same time, a decrease of the high molecular-weight asphaltenes and resins fraction in mixtures results in a decreased viscosity at high temperatures and high shear rates. The optimal composition of mixtures is 1/3 (light/heavy), which provides the decrease of viscosity and suppression of yield stress. (C) 2016 Elsevier Ltd. All rights reserved.

The results of the evaluation of asphaltene content in heavy crude oil depend on the solvent chosen; and the products obtained at this evaluation have varying effects on oil viscosity. In the experiments performed to separate compounds that might be assigned conditionally to the group of asphaltenes, not only standard solvents such as pentane and hexane but also diethyl and diisopropyl ethers as well as hexamethyldisiloxane were employed. The chemical composition of asphaltenes (as estimated using the IR method) depends on the precipitant used. The quantity of precipitated asphaltenes is directly correlated with the energy of the intermolecular interaction of the solvent. In this study, the effects of different “asphaltenes” on oil properties were evaluated by measuring the rheology of the solutions in tetralin at a wide range of temperatures. These solutions demonstrate very different properties (from Newtonian fluid to gel) depending on the concentration. Viscosity depends on the nature of the solvent used to precipitate asphaltenes. Using diethyl ether yields the smallest quantity of asphaltenes but they creates the most viscous solutions. The removal of asphaltenes leads to a significant decrease in heavy oil viscosity. Heavy oil viscosity can be decreased by 2–3 orders. The intensity of the effect is determined by the solvent's solubility parameter.

The miscibility of the bisphenol A epoxy oligomer with a number of aromatic polyethers is studied via optical interferometry. It is shown that polysulfone and polycarbonate are unlimitedly soluble in the oligomer. The dissolution of polycarbonate is accompanied by a chemical interaction and the formation of a new phase. For poly(ether sulfone) and poly(ether imide), amorphous phase separations with the LCST and the UCST, respectively, are observed. The polymer solutions are Newtonian liquids, and the systems in which phase separation occur feature the yield stress. A shift of the phase-equilibrium lines during the action of shear is revealed.

We propose a new alternative method for calculating the resistance of short channels (capillaries) in the flow of viscoelastic polymeric fluids (solutions and melts). The method is based on the assumption that pressure losses in short channels are determined by average time of deformation in passing a fluid through a channel and linear viscoelastic properties of a material. Experiments carried out with a series of moderately concentrated polymer solutions and three polymer melts, as well as literature data, confirmed that pressure losses (expressed via the apparent shear stress at a capillary wall) in flow through capillaries of different length are an unique function of the average residence time in passing through a capillary. Experimental data for every viscoelastic polymeric material form a scaling dependence on the Deborah number calculated as the product of the average residence time and relaxation time found in the periodic oscillation measurements. For different polymeric materials, a master curve can be built by normalizing the apparent shear stress by the characteristic elastic modules at the crossover point. (C) 2014 The Society of Rheology.