Hydrophilic poly-ylids derived from 4,4′-bipyridyl: synthesis, structure and membrane-forming characteristics

Abstract

Interfacial polycondensation of 1,1′-diamino-4,4′-bipyridinium di-iodide, [H 2 N- + NC 5 H 4 -C 5 H 4 N + -NH 2 ]I 2 , with aromatic di- or tri-acyl chlorides, affords a novel class of hydrophilic polymers. These materials are isoelectronic with polyesters but contain ylid linkages [N − -N − -CO] in place of ester bonds [C-O-CO]. Non-crosslinked polymers of this type are insoluble in conventional organic solvents but dissolve readily in proton-donor solvents such as formic and trifluoroacetic acids. Single-crystal X-ray studies of the model oligomer C 6 H 5 CO-N − - + NC 5 H 4 -C 5 H 4 N + -N − -COC 6 H 5 reveal an essentially rigid-rod structure and, in keeping with this, the poly-ylids derived from terephthaloyl chloride and naphthalene-2,6-diacyl chloride exhibit lyotropic liquid crystallinity. Interfacial syntheses of poly-ylids on ultrafiltration membranes afford supported membranes with nodular morphology and useful nanofiltration properties.