Grafted and segmented hydrophilic polyimides for microfiltration membranes: Part I. Synthesis and characterisation

This paper describes the synthesis of two series of hydrophilic copolyimides. Polyimides were prepared with a variety of aromatic units. The copolyimides described are graft and segmented copolymers; the hydrophilic grafts and hydrophilic main-chain segments are both derived from amine-terminated poly(ethylene oxide)s (PEO). Graft copolymers were prepared by reacting mono-amine terminated PEO with pre-formed polyimide having pendant carboxyl groups activated by 1,1-carbonyl diimidazole (CDI). High molecular weight graft copolyimides with significant degrees of grafting were produced using commercial mono-functional Jeffamine®, long-chain PEO; restricted solubility in appropriate solvents limited detailed characterisation. Segmented copolyimides were prepared using Jeffamine diamines in combination with aromatic diamines to form suitable copolymers for use in membrane applications. Equilibrium water uptakes were determined for both grafted and segmented copolyimides. The copolymers were prepared for investigations of fouling in microfiltration membranes the results of which are described in an accompanying paper.