Influence of the chemical structure of terminal groups on the properties of ultrafiltration membranes from polyphenylene sulphone

For the first time, for the problem of high-performance ultrafiltration flat-sheet membranes casting, polyphenylene sulfones (PPSF) with chlorine and hydroxyl terminal groups were synthesized and studied. The synthesis of PPSF was carried out in dimethylacetamide at different ratios of 4,4′-dihydroxydiphenyl and 4,4-dichlorodiphenylsulfone monomers. Two samples with a predominant content of hydroxyl and chlorine terminal groups, PPSF-OH and PPSF-Cl, were studied using NMR, GPC and DSC methods. The coagulation values of polymer solutions in N-methyl-2-pyrrolidone (NMP), the mechanical properties and hydrophilicity of the materials were also determined. Both PPSF samples have high strength modulus (16.0–16.6 MPa). Using the method of deposition in water of PPSF solutions in NMP with PEG-400 additives, flat-sheet porous asymmetric m embranes with a mesoporous (diameter of about 7 nm) thin outer layer and finger-like macropores in the substrate were obtained. An increase in the proportion of –OH terminal groups increases the hydrophilicity of the polymer. This, in turn, made it possible to obtain flat-sheet membranes based on PPSF-OH with a water permeability of 66.1 l/m2 h bar, which is 1.5 times higher than the water permeability of the PFSF-Cl membrane. At the same time, both membranes demonstrate the Blue Dextran (Mw = 70,000 g mol–1) rejection of 99.9%.