Synthesis and characterization of polyoxazoline–polysulfone triblock copolymers

Amphiphilic triblock poly(2-ethyl-2-oxazoline-b-sulfone-b-2-ethyl-2-oxazoline) (PEOX-b-PSF-b-PEOX) and poly(2-ethyl-2-oxazoline-co-ethyleneimine-b-sulfone-b-2-ethyl-2-oxazoline-co-ethyleneimine) (PEOXcoPEI-b-PSF-b-PEOXcoPEI) copolymers were synthesized for potential use as water purification membranes. Poly(arylene ether sulfone) (polysulfone) oligomers of controlled molecular weight were prepared by nucleophilic step polymerization of 4,4′-dichlorodiphenyl sulfone with a molar excess of bisphenol-A. The phenolate endgroups were then reacted with ethylene carbonate to afford telechelic aliphatic hydroxyethyl groups. These were tosylated to produce macroinitiators for ring-opening cationic polymerization of 2-ethyl-2-oxazoline. Subsequently, the pendent amides on the hydrophilic PEOX blocks were also hydrolyzed to generate positively charged PEOXcoPEI-b-PSF-b-PEOXcoPEI copolymers. Compositions with high polysulfone compositions relative to the hydrophilic blocks were of particular interest because they maintained good mechanical integrity in water. Water uptake at room temperature increased up to 18 wt% for copolymers with 22 wt% of the hydrophilic components. Solid-state thermal properties suggested some phase mixing of the components in the PEOX-b-PSF-b-PEOX copolymers but better phase separation of the blocks in the partially hydrolyzed PEOXcoPEO-b-PSF-b-PEOXcoPEI materials.