Cross-Linked Quaternized Poly(styrene-b-(ethylene-co-butylene)-b-styrene) for Anion Exchange Membrane: Synthesis, Characterization and Properties

Poly(styrene-b-(ethylene-co-butylene)-b-styrene) triblock copolymer (SEBS) was selected for functionalization and cross-linking reaction to prepare the anion exchange membrane. The cross-linked quaternized SEBS (QSEBS-C-n) membranes were synthesized by simultaneous of quaternization and cross-linking of chloromethylated SEBS with alpha,omega-difunctional tertiary amines. The spacer groups of (-CH2-) in diamines did affect the functionalization, micromorphology and properties of the resulting QSEBS-C-n membranes. The ionic conductivity of QSEBS-C-n membranes greatly increased and methanol resistance slightly decreased with increasing the length of spacer groups in the cross-linked structures from -(CH2)- to -(CH2)(6)-. Compared to the un-cross-linked QSEBS, the QSEBS-C-n membranes behaved much higher mechanical property, service temperature, chemical stability and thermal stability. Moreover, the hybrid composite membrane of QSEBS-C-6 with 0.5% of graphene oxide could also be in situ prepared. This hybrid membrane had both relatively high ionic conductivity of 2.0 X 10(-2) S.cm(-1) and high selectivity of 7.6 X 10(4) S.s.cm(-3) at 60 degrees C due to its low methanol permeability.