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20 “Application of interferometry to analysis of polymer-polymer and polymer-solvent interactionsстатья
- Авторы: Veronica Makarova, Valery Kulichikhin, Ch
- Сборник: in Interferometry: research and applications in science and
- Год издания: 2012
- Первая страница: 393
- Последняя страница: 436
- Аннотация: The different kinds of phase equilibria (amorphous, crystalline, liquid-crystalline) are considered. Each of them has definite futures that were analyzed on examples of variouspolymer-polymer and polymer-solvent systems. All above mentioned results relate to thermodynamic properties for binary systems containing polymers, and all of them were obtained by interferometry method. In addition to thermodynamic data, this method gives information about kinetics of components interactions that allows us to measure simultaneously interdiffusion coefficients. This dualism of optical interferometry method in application to interaction in polymer containing systems is its great advantage. That why its application in scientific practice is very useful and fruitful. The couple PC – low molecular weight PMMA is a good example of polymer system with amorphous phase equilibrium. Method of interferometry is very useful and fruitful for such kind of systems due to informativity and combination of joint approaches: kinetics of mass11 transfer and thermodynamics of phase states. Increase of the mutual solubility with temperature indicates on UCST that could not be measured experimentally but was calculated using evolution of the interaction parameter with concentration. Comparison of the phase diagram with concentration dependence of viscosity allowed us to observe local minimum of viscosity near the binodal (sooner in meta-stable region between bimodal and spinodal where microemulsion appears as the first step of the phase decomposition) and to apply the empiric equation for calculation of the blends viscosity by means of accurate determination of the composition from binodal branches. Joint consideration of diffusion and rheological properties seems to be important for judging about structure, kinetic and thermodynamic behaviors of complex, multiphase polymer systems. This approach will be used further for analysis of systems with LC and crystalline equilibria. Calculations of the interphase layers thickness depending on dimensions of drops and time, based on knowledge of interdiffusion coefficients can be very useful for correct organization of technological process of mixing and, consequently, development of new materials with three-phase structure and new properties. Several examples of crystalline equilibrium in couples polyester-polyester are considered a well. The neat polymers are semi-crystalline and phase equilibrium for their pairs is describing by liquidus lines, sometimes with eutectic points. But this situation takes place at T<280-290oC, when chemical interaction can be neglected. The original feature of these data consists in using as one component of pair thermotropic LC polyesters and copolyesters. Up to clearing point of LC component the interdiffusion process is registered using one part of the interference patterns. Such approach was demonstrated first time. At using LC polymer melt as one component, both interdiffusion process and ester-ester exchange is delayed because of high molecular orientation in LC polymer along interface. This dense layer prevents fast penetration of coil-like macromolecules of isotropic polyester melt. But in the case of PET-PEN pair both polymers both melts are isotropic and transparent, that is why interaction process can be visualized easy. The hypothetic mechanism of joint action of physical and chemical interaction is proposed. The first stage is diffusion, but after penetration of macromolecules of one polymer into another the trans esterification starts and transition between these two processes can be estimated from kinetics of movement of isoconcentration planes. Method of optical interferometry is not so often used for describing phase equilibria in solutions of stiff-chain polymers forming in solutions LC phase. In this part was shown its application for several solutions the same polymer in different solvents. We were wonder toinformativity of in 1 terferometry for such systems. The main portion of equilibria lines in solutions were detected by interferometric method. Of course, for LC systems method of polarizing microscopy has to be obligatory supporting method for confirmation of the LC phase existence. In addition, viscometry seemed to be very useful again not only for description of features of these systems at flow, but also for additional detection of LC transitions as well as for formation of CS phase. As opposed to diagrams obtained for other systems, for which two types of phase equilibrium are located in different concentration regions, in the case of aqueous systems, all transitions, including formation of crystal solvates, take place below the convex part of the binodal, that is, at the same concentrations but at different temperatures. This result indicates that the activity of water with respect to formation of hetero H-bonds tends to increase with a decrease in temperature.
- Добавил в систему: Куличихин Валерий Григорьевич