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Perfluorinated polyesters (PFPE) are used as components of high-performance lubricants and oils operating in high and low temperature conditions, including in special-purpose products used in space and in Arctic conditions. To date, the methods for producing PFPE are complex processes that are quite demanding to the conditions of synthesis, which makes it almost impossible to produce these compounds commercially on a large scale. One of the promising approaches to obtaining perfluorinated esters is liquid-phase direct fluorination. Toxic, ozone-depleting solvents have been used in these processes. When they are replaced with harmless, perfluorinated liquids, for example, perfluorodecalin (PFD), another problem is found – the original polyesters are insoluble in PFD, which is confirmed by laser microinterferometry. In this regard, ultrasonic dispersion of the initial polypropylene glycols (PPGs) of various molecular weights in PFD was proposed in order to obtain emulsions for subsequent direct fluorination. The resulting emulsions were studied using gel-penetrating chromatography, dynamic light scattering and gravimetry. According to the results of the study, the values of particle sizes and emulsion concentrations were obtained over time after ultrasound, and it was also concluded that the stability of the molecular weight of PPG in the emulsion after sonification. The applicability of ultrasonic dispersion for a high specific surface area of the phase boundary in the PPG – PFD system is discussed, and the feasibility of sonification in a continuous or batch mode when implementing liquid-phase fluorination of PPG in PFD is also discussed.

Silicone resins are hyperbranched macromolecules, which are nearly spherical in shape, nanometer in size, and covered with numerous terminal organic groups. For this reason, they can play a role of functionalized silica nanoparticles that are miscible with a polymer medium. In this paper, mixtures of linear polyisobutylene (PIB) with methyl-terminated silicone MT resin are considered. The phase states of mixtures were studied by laser interferometry method accompanied with rheological tests. It turned out that the solubility of the silicone resin in PIB matrix does not exceed a few percent even at high temperatures. Nevertheless, the addition of the resin significantly reduces the effective viscosity of PIB due to the shear-induced interlayer slip. To describe the concentration dependence of the blend viscosity, various empirical equations were considered, and their combination to describe the viscosity of blends in different phase states by one equation was proposed.

High free volume glassy polymers or polymers of intrinsic microporosity such as poly[1-trimethylsilyl-1-propyne] (PTMSP) and polybenzodioxane (PIM-1) are extra high gas permeability membrane materials. One of their major drawbacks is low gas selectivity. In this study, thin film composite (TFC) membranes have been developed with high CO2 permeance and superior CO2/N2 selectivity due to a strong synergistic effect. The TFC membranes, comprising a thin layer (0.29–0.42 μm) of PIM-1 atop a cross-linked PTMSP gutter layer (2.07–3.44 μm) on a porous backing material, were fabricated by coating PIM-1 solution on the cross-linked PTMSP support. A key element is that for coating PIM-1 a mixed solvent of chloroform and trichloroethylene (1 : 1) was successfully implemented for the first time. All membrane samples demonstrated a strong synergistic enhancement of CO2/N2 selectivity (α = 35.8–55.7) compared to PIM-1 (α = 18.5) and cross-linked PTMSP (α = 3.7). SEM, TEM and laser interferometry studies revealed that the synergistic enhancement of gas selectivity in the TFC membranes is most likely due to the creation of a very thin boundary layer between PIM-1 and the cross-linked PTMSP gutter layer. The aged TFC membranes (after three months) showed a severe drop in gas permeance while keeping nearly the same high selectivity. Thus, future success in the prevention of polymer physical aging, together with the synergy effect in selectivity reported for the first time in this work, will give new opportunities for application of polymers of intrinsic microporosity.

Phase separation of polymer solutions initiated by the addition of a nonsolvent is the main method for the preparation of polymer membranes. Depending on the application, such membranes must have a different pore size, which depends on the numerous parameters of the forming process. The liquid–liquid phase separation has been considered for cellulose solutions in N-methylmorpholine N-oxide (NMMO) interacting with various alcohols (methyl, ethyl, isopropyl, and isobutyl). Kinetics of cellulose regeneration was investigated by laser interferometry technique to understand the mechanism of cellulose film structure formation in the NMMO process. Influence of temperature, coagulant nature, and cellulose content on the process kinetics and morphology of the films was studied and corresponding interdiffusion coefficients were calculated. Based on the solubility parameters, triple phase diagrams of the systems were calculated. Formation of different morphologies was explained primarily by the different position of the composition path, the bimodal curve, and the gelation line in the phase diagrams. The second important parameter was the different rate of mutual diffusion of the NMMO and coagulants, due to the difference in the viscosity of the latter. Using methanol or ethanol as coagulation baths leads to obtaining the nanoporous structure of cellulose films, whereas isopropanol and isobutanol favors macropore formation.

In the current work, porous films based on epoxy resin have been obtained via the Breath Figures method. It was shown that the use of a low-temperature curing agent and fluoro-containing organosilicon copolymer, compatible with epoxy resin, makes it possible to obtain porous, thermostable, highly hydrophobic coatings with a pore diameter of 3–4 µm. When the epoxy resin/copolymer mixture is homogenous, the modifier prevents water droplet coalescence; otherwise, the mixture becomes heterogeneous, and the positive influence of the modifier is lost. The obtained modified porous films are highly hydrophobic and maintain their porous structure until polymer devitrification occurs. The simplicity of the Breath Figures method shows great potential for the manufacture of water-repellent paint coatings based on epoxy resin for use in a variety of applications.

Highly concentrated solutions of acrylonitrile copolymers (PAN) in N-methylmorpholine N-oxide (NMMO) were obtained via the solid-phase activation method. Specific interactions in the system at different stages of the dissolution process starting from solid-state activation and finishing with a transition to a viscous state were studied by IR spectroscopy, polarizing microscopy, interferometry and rheology. It was shown that the crucial factor determining a possibility of dissolution is the complex formation between carboxyl groups in the copolymer and the electron-donor N → O group in the solvent. This complex arises during the process of solid-phase activation of PAN and crystalline NMMO, which thereafter melts and transforms into a homogeneous solution having viscoelastic behavior. In the temperature range of 130–135 °C, irreversible chemical transformations take place in the solutions due to the coherent interaction between nitrile groups; these reactions lead to the formation of cyclic structures and conjugated sequences in the PAN chains. Rheological properties follow this process via specific viscosity and viscoelasticity evolution in time.

Phase change materials based on paraffin wax are characterized with low thermal conductivity, which could be improved by the addition of particles of a heat-conducting material, for example, graphite. However, graphite particles agglomerate in molten paraffin wax matrix and settle. In this study, the use of hydrophobic nano-sized silicon dioxide as a stabilizer was considered to obtain stable dispersions of graphite in paraffin wax. Rheological and thermophysical properties of paraffin-based mixtures containing from 1 to 5 vol. % of hydrophobic silica and from 1 to 15 vol. % of graphite were investigated. At the concentration of 3 vol. %, silica nanoparticles form a percolation structure, which is expressed in the emergence of the yield stress that is capable to prevent the sedimentation of graphite particles introduced into the mixture. It allows obtaining dispersions that are stable both in time and at passage of cooling–heating cycles. The joint influence of silica and graphite fillers on the ability of paraffin wax to accumulate and conduct heat was investigated. Thermal conductivity of dispersions at the introduction of graphite increases according to the Maxwell's model, which allows improving the thermal conductivity on 33 % from initial value at the introduction of 15 vol. % of graphite.

Phase behavior, rheology and adhesive properties of polyisobutylene-based blends containing up to 60 wt% of polyethylene wax were studied. Polyisobutylene and wax partially dissolve in each other at high temperatures, which strongly reduce the viscosity of the blends and facilitate their mixing. When cooled, the wax loses its solubility in the polymer matrix and crystallizes to form reinforcing particles. These particles increase the viscoelasticity of the blends, resulting in improved durability (up to 66-fold) and strength (up to 1.4-fold) of adhesive bonds. At the same time, the growth of viscoelasticity does not lead to a loss of tackiness of the blends, as the application of external force to form an adhesive bond destroys the percolation structure of wax particles. Because of the low specific surface area of wax particles, they increase the durability of adhesive joints worse than silica (in 380-fold) or organoclay particles (in 3300-fold). However, the use of polyethylene wax allows reducing melt viscosity by 4–5 decimal orders of magnitude in the case of highly filled adhesives.

It is obvious that polymers of the similar composition but with different molecular weights are miscible, but what will happen if one of them is linear and another one has branched architecture? In this paper, mixtures of linear polydimethylsiloxane (PDMS) with methyl-terminated silicone MT resins are considered. Since these resins consist of hyperbranched macromolecules with nearly spherical shape and nanoscale diameters, they are both macromolecules and colloid particles at the same time. The phase states of mixtures were studied by laser interferometry method accompanied with rheological tests. The effect of molecular weight of resins and their terminal groups on miscibility was demonstrated. The methyl-terminated resins with low molecular weight are well miscible with linear PDMS macromolecules but immiscible blends are formed in the case of resin's high molecular weight. The rheology of the blends is determined by their phase state, which depends on the ratio of components and temperature. For homogeneous resin/PDMS mixtures, a slight positive deviation of viscosity from the log-additivity rule is inherent, whereas heterogeneous blends are similar in rheological behavior to a gum. Various empirical equations are considered for describing the viscosity-composition dependence; as a result, their unification to characterize blends with different phase states was proposed.

The extension rheology of polymer/layered silicate composites based on liquid-crystalline (LC) solution of hydroxypropylcellulose (HPC) in oligomeric polyethyleneglycole (PEG) was studied. The HPC concentration was 60 wt%. Extension experiments have been carried out for materials in the different phase states. Compositions containing Na-montmorillonite (MMT) were prepared by a two-stage method. Final systems may be attributed to solutions of HPC in PEG, which intercalates into MMT galleries. The ordered domain structure of the LC matrix as well as hydrogen-bonded network between HPC and PEG molecules significantly reduce deformation at break and provide a strong nonlinear viscoelastic behavior at extension. Appearance of isotropic phase in solutions leads to a sharp drop of the elongation viscosity. The introduction of clay into LC solution only slightly affects the viscosity value but significantly suppresses the strain-hardening scale. In contrast, loading in biphasic state of HPC-PEG solution with even small amount (1 wt%) of MMT leads to the drastic viscosity increase that does not change in further growth of the filler concentration. Elastic properties of the systems under study demonstrate the similar behavior. This effect likely is caused by the interrelationship between deformability of the LC domain structure and the network strength formed by the clay particles. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers

We have analyzed the thermal conductivity and the tensile modulus of composite materials within the framework of the Halpin-Tsai and Lewis-Nielsen models. The parameter linking thermal conductivity and tensile modulus together is the shape factor of the (nano)filler. Model analysis based on experimental data shows that particle aggregation into a weak mechanical network may be required to achieve good correlation between thermal conductivity and the Young’s modulus when analyzing the data within the framework of a single model and requiring the same value of the shape factor. We believe this approach will make quantitative analysis of nanocomposite thermal properties possible.