Abstract
Polymer film membranes are used to solve specific separation problems that dictate structural requirements. Structural and morphological parameters of film membranes based on glassy polyheteroarylenes can be controlled in the process of preparation from solutions that opens up prospects for obtaining structured membranes required for targeted separation. In the case of aromatic poly(amide-imide)s, the possibility of controlling film formation and structure virtually has not been studied. In the present work, a series of homologous co-poly(amide-imide)s differing in the number of repeating units with carboxyl-substituted aromatic fragments was synthesized by polycondensation. Comparative analysis of the processes of formation of membranes with different morphologies based on these polymers under equal conditions was performed. New information was obtained about the influence of the amounts of carboxyl groups and the residual solvent on structural properties of asymmetric membranes. The influence of these factors on transport properties of dense membranes under pervaporation conditions was studied. It was demonstrated that in the case of carboxyl-containing poly(amide-imide)s, the domains formed during film preparation had a significant effect on membrane properties.
Highlights
Aromatic poly(amide-imide)s (PAIs) have proven to be promising membrane-forming polymers [1–14]
After removal of the soldiaminodiphenyl ether and 3,5-diaminobenzoic acid were dried for 48 h; the reagents vent, dried the polymer in the form of a powder was studied by frustrated total internal reflection (FTIR)
Since the same starting solutions were used in preparation of samples of different types, it became possible to perform comparative analysis of polymers and to reveal the contribution of carboxyl-containing fragments to structural and transport characteristics of the produced membranes
Summary
Aromatic poly(amide-imide)s (PAIs) have proven to be promising membrane-forming polymers [1–14]. Our earlier research has shown that under the same conditions, poly(amide-imide)s containing different diamine components in macrochains gave structurally different asymmetric microporous membranes characterized by similar morphologies in the skin layer area [8,14,16,17]. When a mixture of precipitants was substituted for precipitation baths, no major changes in film morphologies were observed In this case, a wide area with smaller pores appeared near the skin layer; these pores were elongated towards the upper surface. For PAI-2, water is a softer precipitant than for PAI-1 This leads to the formation of asymmetric porous structure with thicker pore walls and skin layer. New copolymers containing fragments of 4,40 -diaminodiphenyl ether and 3,5-diaminobenzoic acid in different ratios were synthesized; the influence of carboxyl-containing fragments on structural, morphological, and transport properties of continuous nonporous and phase-inversion PAI membranes was investigated. In the experiments, distilled water (pervaporation study) and deionized water (contact angles measurements) were used which is obtained on a laboratory installation immediately before the study
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