-The approach to the prediction of permeability of polymer membranes based on polyimides and polyamidoimides towards helium is described. According to the approach, the activation energy of helium penetration is expressed by a relationship involving the van der Waals volume of the repeat unit and a set of atomic parameters characterizing the contribution of each of the atoms and intermolecular interaction types into the value of activation energy. The contributions of the imide cycles, type of the connection (meta-, para-, or ortho-), and of the CF3, CH3, CO, Cl, F, and SO2 polar groups have been accounted for. Repeated solution of the redundant set of equations obtained on the basis of the proposed relationship has afforded the parameters giving the correspondence of the calculated values and the experimental data on the membranes permeability with correlation coefficient 0.965. Hence, the possibility to search for the structures of polyimides and polyamidoimides with the target permeability without laborious and expensive experiments has been demonstrated.

Investigations carried out in recent years on the development of models and computer programs for predicting and analyzing the physical properties of polymers are described. The method for constructing diagrams of compatibility of water permeability and the glass transition temperature, density, the thermal expansion coefficient, the cohesion energy, etc. is analyzed. Computer synthesis of network polymers and the possibility of predicting the thermal expansion coefficient of materials based on polyvinyl chloride and the elastic modulus of composites with a number of aromatic polymers are considered. The effect of a solvent (plasticizer) on strength and viscosity is analyzed. Considerable attention is paid to the use of self-oscillations excited during deformation of polymer films in actuators of nanomechanical devices. The calculation of the viscosity of dispersions of spherical nanoparticles with an adsorption polymer layer in a polymer melt and in a low-molecular liquid is carried out. The principles of predicting the coefficients of molecular packing of amorphous-crystalline polymers and their solvents are stated, and the influence of the chemical structure of heat-resistant thermoplastics on friction against steel is also estimated.

Изложен подход к прогнозированию проницаемости для гелия полимерных мембран на основе полиимидов и полиамидоимидов различного строения. Согласно этому подходу, энергия активации процесса проникновения гелия описывается соотношением, в которое входят ван-дер-ваальсов объем повторяющегося звена полимера и набор атомных констант, характеризующих вклад каждого атома и типа межмолекулярного взаимодействия в величину энергии активации. Учитывается вклад имидных циклов, количество ароматических ядер и тип присоединения ( мета -, пара -, орто -), вклад полярных групп CF 3 , CH 3 , CO, Cl, F, SO 2 . Неоднократное решение избыточной системы уравнений, построенной на основе предложенного соотношения, позволило определить константы, приводящие к согласию расчетных и экспериментальных данных по проницаемости мембран с коэффициентом корреляции 0.965. Таким образом, показана возможность поиска структур полиимидов и полиамидоимидов с заданной проницаемостью для гелия без длительных и дорогостоящих экспериментов.

A model was proposed for constructing the diagrams of compatibility of the water permeability of polymers with their physical characteristics such as van der Waals volume, density, glass transition temperature, intense thermal degradation onset temperature, and cohesion energy. A computer program that allows constructing such diagrams in automatic mode was developed. It was shown that, for polycarbonates, there exist a huge number of structures with relatively low water permeability. The choice of structures with high water permeability is significantly limited. For substituted polystyrenes the number of structures with both high and low water permeability is limited. The reason is that the repeating units of polymers of this group are synthesized from two basic fragments, while those for the rest of the polymers, from five or more basic fragments.

The application of carbon nanoparticles as modifiers of polyepoxyurethane-containing isocyanurates results in achieving the highest increase in physicochemical properties even when they have a low content in the composition. Impact number A at nanocarbon weight content W of 0.5% is almost 1.5 times higher than that of the matrix polymer. The obtained dependence of the impact number on the weight content A = (W) for the considered nanocomposite samples has an extremum pattern, where the maximum is achieved at W = 0.5%. At W = 0.5%, elasticity modulus Ecomp of the composite (in compression tests) increased almost 1.3-fold compared to the starting polymer.

Currently, methods for predicting the properties of polymers are very popular, since they simplify the work of synthetic chemists. Instead of lengthy and time-consuming experiments, many properties of polymers can be predicted in advance based on their chemical structure. Naturally, such tasks must be computerized so that the properties are predicted after the chemical structure of the repeating polymer unit is displayed on the display screen. This is the so-called direct task. The inverse problem is more complex and interesting. It consists in entering the intervals of the desired characteristics into the computer. Then computer synthesis of polymers possessing these characteristics are realized. The work consists in writing a computer program that allows the computer synthesis of polymers of different classes with specified intervals of water permeability. These classes include polyurethanes, polysulfones, polysulfides, polyethers and polyesters, polyamides, polyketones and polyethyrketones, polycarbonates, polyolefins, vinyl polymers, polystyrene, acrylic and methacrylic polymers. On the basis of this program, water permeability compatibility diagrams are constructed with various physical characteristics of polymers – glass transition temperature, temperature of the onset of intensive thermal degradation, cohesion energy, density, solubility parameter (Hildebrand parameter).

There are a number of tasks that require the creation of executive micro - or nanomechanical devices that allow you to convert one type of mechanical movement (for example, displacement) into another (for example, into oscillatory). Such devices that convert the energy of the input signal (electrical, optical, mechanical, etc.) into an output signal (for example, in controlled motion) are called actuators. Work on the creation of actors is underway in the UK, USA, Japan and a number of other countries. There are prototypes of actuators, but the problem of their autonomy has not yet been solved. In order for the actuator to become a real device suitable for practical use, it is necessary to solve a number of fundamental issues (to develop microminiature energy sources for their drive; to determine the methods and modes of activation of actuators that generate vibrations). Existing experimental and theoretical research in the field of self-oscillation of polymers allows us to hope for a solution to these problems in a simpler way. The studies performed below show that in accordance with the proposed rules for the selection of polymers for actuator drive polymethyl styrene and polycarbonate can be used as polymer systems in which self-oscillations will be excited in the frequency range of 200–250 Hz. The stretching rates at which the self-oscillations of the above polymers begin to be excited have been determined. The heat generated in this case can be used to maintain self-oscillations for a long time. The proposed approach can be considered as an alternative to mechanochemical actuators using methanol as a fuel. The ways of increasing their operating time and thermal effects when self-oscillations are excited in the frequency range of 200–250 Hz are considered.

— Different trends observed during cryotropic gelation of 8% poly(vinyl alcohol) aqueous solutions (preheated to 25, 55, and 85°С) at rapid cooling and freezing of the system have been examined. The data of rheology, thermomechanical analysis, attenuated total reflection, and scanning electron microscopy have revealed that the macroporous poly(vinyl alcohol) cryogels formed under above conditions differ in elastoplastic properties, swelling ability in water, degree of microcrystallinity, and pores size. The obtained results have been confirmed by the study of diffusional release of stabilized silver nanoparticles from the cryogels. It has been shown that the macropores walls in the cryogel network consist of spherical formations, likely contacting microgel particles formed during the liquid-phase separation of the polymer solution prior to the cryotropic gelation stage.

One of the possible approaches to the analysis of a physical mechanism of time dependence for the resistance coefficients of materials is suggested. The material durability at the constant stress is described using the Zhurkov and Gul' equations and the durability at the alternating stress—using the Bailey criterion. The low strains lead to structuring of a material that is reflected in a reduction of the structure-sensitive coefficient in these equations. This affords 20% increase in the durability. The dependence of the resistance coefficient assumes an extremal character; the maximum is observed at the time to rupture lg tr ≈ 2 (s).

Measurements of stress relaxation of two samples of decking boards after exposure in rain and chlorinated water, in ice, and in a mixture of gasoline and water in different concentrations from 1 to 7% were carried out. Samples consisting of 60% wood flour, 30% polyvinyl chloride and 10% additives were used for measurements. Additives are flame retardants, stabilizers, modifiers and dyes. The mineral filler CaCO3 was used as modifier. In sample No.1, the CaCO3 content was 42% and the wood content was 18%. For sample No.2, the CaCO3 content was 24% and the wood content was 36%. As a result of measurements after exposure for 200 days, it was found that the relative drop in mechanical stress decreases when the mineral filler is added to the composition. The nonlinear mechanical behavior for the initial sample No.1 is observed at 2% strain, and for the sample No.2 – at 3% strain. When aged in chlorinated water and in ice, the nonlinear mechanical behavior is observed for all deformations. The generalized relaxation curves indicate that decking boards can be used with confidence for a long time.

New models and calculation schemes have been developed for the quantitative analysis of a number of physical properties of polymers glass transition temperature, flow temperature of polymer nanocomposites, thermal conductivity, boiling point of polymer solutions, water absorption and water permeability of polymers and nanocomposites, strength, viscosity, storage and losses moduli, refractive index and dielectric constant. All calculation schemes are based on the structure of linear and cross-linked polymers; their degree of crystallinity, free volume, the effect of temperature, the composition of copolymers and homogeneous mixtures of polymers, the concentration of nanoparticles, their shape, size distribution, orientation angles, the structure of polar groups grafted to the surface of nanoparticles, the energy of intermolecular interactions are taken into account. All computational schemes are computerized and allow calculations to be carried out automatically after the introduction of the structure of a repeating unit of polymer unit into the computer, as well as the shape and size of nanofillers.

Abstract The possibility of predicting the coefficient of thermal expansion for the blends of polyvinyl chloride (PVC) with a number of organic polymers is shown. It was found that the higher the glass transition temperature of the polymer, the lower the coefficient of thermal expansion of the mixture of PVC with this polymer. The dependence of thermal expansion for composites based on wood of different species and bamboo is also analyzed. In all cases, the coefficient of thermal expansion is reduced, which allows the use of forecasting results for the development of new PVC-based building materials with improved thermal properties.