Highly ordered ion-conducting block copolymers by hydrophobic block modification
Block copolymer-based AEMs provide advanced materials with tunable properties through manipulation of both the ionic domains for high conductivity and the hydrophobic domains for mechanical integrity. Herein, we describe the ionic conductivity and self-assembly behavior of cationic block copolymers based on quaternized vinyl benzyl chloride (QAVBC) by tuning the hydrophobic block composition with hexyl methacrylate (HMA), lauryl methacrylate (LMA), stearyl methacrylate (SMA), and 4-butylstyrene monomers (BS). The block copolymers showed self-assembly of highly-ordered microstructures as confirmed by small angle X-ray scattering and transmission electron microscopy. A non-ionic block copolymer composed of PVBC100-b-PBeS183 showed less ordered phase separation compared to the quaternized PQAVBC100-b-PBeS183 sample. The PQAVBC100-b-PBeS107 and PLMA68-b-PQAVBC129 samples with long-range ordered microstructures had approximately three times higher conductivity than that of the less-ordered non-block copolymer based quaternized poly(arylene ether ketone) with a similar ion exchange capacity (∼2.8 meq. g−1). Moreover, the robust anionic PQAVBC44-b-PBS202 block copolymer immersed in liquid water had an ionic conductivity three orders of magnitude greater than the samples under 95% relative humidity conditions due to the increased water uptake of the material under liquid conditions.