Gas diffusion characteristics as criteria of nonequilibrium state of amorphous glassy polymers

The Effect of Conformation Order on Gas Separation Properties of Polyetherimide Ultem Films

“…For gas separation experiments: As-cast film formation by solvent evaporation (see above); 12% to 13% of residual chloroform is fixed in films in these conditions [ 22 ]; Annealing at 10–20 °C above the glass transition temperature [ 12 , 22 ]; C 2 H 5 OH treatment—swelling in ethanol for one day with further evacuation [ 12 , 19 ]; sc -CO 2 treatment—swelling in sc -CO 2 for 4 h at 120 °C and 450 atm. …”

“…Thermodynamic nonequilibrium state of glassy amorphous polymers leads to a change in nonequilibrium free volume and consequently gas separation properties of polymer membranes during exploitation due to physical aging [ 1 , 9 , 10 ] or plasticization with a separated component [ 1 , 11 ]. On the other hand, this is why gas separation characteristics might be considered as a nonequilibrium level assessment criterion for polymer film, prepared by one method or another [ 12 ]. As there are no direct methods of measurement for chain packing ordering for X-ray amorphous polymers, a combination of analysis of gas diffusion coefficients [ 12 ] with the results of other methods can be promising for the determination of a trend for a change of chain packing ordering and the effect of this trend on physicochemical and transport properties.…”

“…On the other hand, this is why gas separation characteristics might be considered as a nonequilibrium level assessment criterion for polymer film, prepared by one method or another [ 12 ]. As there are no direct methods of measurement for chain packing ordering for X-ray amorphous polymers, a combination of analysis of gas diffusion coefficients [ 12 ] with the results of other methods can be promising for the determination of a trend for a change of chain packing ordering and the effect of this trend on physicochemical and transport properties. One of these methods is vibrational spectroscopy, which provides evaluation of conformational structure change on atomic level and molecular level.…”

“…It is well known that polymer treatment with sc -CO 2 facilitates desorption of a residual solvent [ 21 ] independently of its capability to form hydrogen bonds with polymer functional groups. However, according to the authors of [ 12 ], such film treatment can lead to increase of chain packing ordering in polyetherimides. Nevertheless, there has been no confirmation of changes of conformational chain ordering after amorphous polymer film treatment with sc -CO 2 obtained by other methods.…”

“…Quantitative criteria of amorphous polymer chain packing ordering are proposed for PEI Ultem ( Scheme 1 ) based on analysis of structural characteristics from IR spectra of polymeric films at different formation and treatment conditions and diffusion coefficients of non-condensable gases (H 2 , He, N 2 , O 2 , CO 2 , and CH 4 ). Formation of hydrogen bonds has been noted earlier for this polymer [ 13 , 15 ], and quantitation of chain packing ordering change has been performed using gas separation characteristics analysis [ 12 ] at different film formation and treatment conditions.…”