ИСТИНА

The most progress in membrane science for the last decades was achieved in a field of the relationship between chemical structure of materials for gas separation and their gas permeation parameters. But, there is a lot of facts that not only chemical structure, but also an ordering of the macromolecular structure can affect significantly the permselectivity of polymers [1, 2]. The objects of the present work are two amorphous polyetherimides (PEI) with constrained elasticity properties. Gas transport parameters of the both polymers (Table 1) [2, 3] were measured under different film forming conditions: 1. Drying up to constant weight under vacuum; 2. Strained aging or keeping in strained state for a prolonged period (2-3 months) at room temperature. The strain appears due to contraction of the film fixed at perimeter during the process of slow solvent evaporation; 3. Biaxial deformation due to compression of drying film between two plastic Pb-Sn alloy metal discs with controlled degree of deformation. 4. Annealing above the glass transition temperature for 2 hrs. The films of the both polymers were undergone biaxial deformation procedure (up to 40%). Then, gas transport parameters of those and initial films were measured. Some of the data are presented in Reytlinger-Robeson diagram for O2/N2 pair. The growth of permselectivity of PEI 1 from state “drying” to “strained aging” was explained previously by ordering of polymer chains due to aging in strain conditions in presence of residual solvent. Although the both polymers have similar chemical structure behavior of their O2/N2 transport properties after biaxial deformation is rather different. Namely, for PEI 2, no change of permselectivity is observed as the deformation degree of the films increases. Oppositely, for PEI 1 films undergone deformation one can see a somewhat increase of O2/N2 permselectivity whereas permeability coefficients of oxygen keep almost constant value. The same trends on permselectivity – permeability diagrams are observed for other gas pairs. They can be explained by different modification of free volume distribution in the polymer films through the process of biaxial deformation. As a result, molecular free volume distribution of PEI 1 becomes more ordered [2] and gas selective [1 – 3].This and other possible explanations will be discussed in the presentation. 1. Alentiev A, Yablokova M, Lazareva Yu, Vidyakin M, Kostina Yu, Yampolskii Yu, Antipov E, Rusanov A, Ronova I, Kuznetsov A, Bruma M (2008) Thermostable polymers for membrane gas separation: influence of supramolecular structure on permselectivity 8th International Symposium on Polyimides High Polymers-Stepi 8 Montpellier, 9-11 June 2008:458 2. Yuri Yampolskii, Alexandre Alentiev, Galina Bondarenko, Yulia Kostina, Matthias Heuchel, Intermolecular Interactions: New Way to Govern Transport Properties of Membrane Materials, Ind. Eng. Chem. Res. 2010; 49: 12031–12037 3. J. Kostina, G. Bondarenko, O. Raitman, A. Alentiev, A. Rusanov The effects of interactions with solutes on membrane properties of polyetherimides: FTIR, ТМА and quantum chemical investigation. Polytech’Monpellier, Universite Montpellier II, S.T.L. June 9-11,2008, p 437-446