Aluminum-Neutralized Sulfonated Styrenic Pentablock Copolymers with
Excellent Water Transport and Mechanical Properties

We investigate the effects of neutralization with Et3Al on morphologies of a poly(t-butylstyrene-b-hydrogenated isoprene-b-sulfonated styrene-b-hydrogenated isoprene-b-t-butylstyrene) (tBS-HI-SS-HI-tBS) pentablock copolymer solution in a non-polar solvent mixture and a membrane cast from this micellar solution. Upon neutralization the HI–tBS blocks expand to increase the corona thickness. The diameter of micelle core (2R) increases slightly (5%) upon neutralization, while the closest approach distance between cores (2RCA) increases ~20%.  Both the acid-form and aluminum-neutralized membranes exhibit bicontinuous morphology with interconnected SS microdomains based on X-ray scattering and TEM results. The aluminum-neutralized membrane with continuous SS microdomains shows excellent water transport properties that are comparable to the acid-form membrane. The strong interaction (cross-linking) between Al(3+) ions and the oxygen center in the sulfonic acid in the aluminum-neutralized membrane restricts water uptake and provides much improved mechanical properties and better dimensional stability. This study demonstrates that the understanding of the structure–property relationships is a key part of the development of new membranes with improved properties.


J.-H. Choi, C. L. Willis, K. I. Winey*, Journal of Membrane Science, 428, 516–522, 2013.
“Effects of neutralization with Et3Al on structure and properties in sulfonated styrenic pentablock copolymers.”