Triblock and diblock copolymers based on isoprene (IP) and chloromethylstyrene (CMS) were synthesized by sequential polymerization using reversible addition-fragmentation chain transfer radical polymerization (RAFT). The block copolymers were quaternized with tris(2,4,6-trimethoxyphenyl)phosphine (Ar3P) to prepare soluble ionomers. The ionomers were cast from chloroform to form anion exchange membranes (AEMs) with highly ordered morphologies. At low volume fractions of ionic blocks, the ionomers formed lamellar morphologies, while at moderate volume fractions (≥30% for triblock and ≥22% for diblock copolymers) hexagonal phases with an ionic matrix were observed. Ion conductivities were higher through the hexagonal phase matrix than in the lamellar phases. Promising chloride conductivities (20 mS/cm) were achieved at elevated temperatures and humidified conditions.
Bibliographical noteFunding Information:
The authors gratefully acknowledge financial support from the Army Research Office through a MURI award, W911NF-10-1-0520, and the central analytical facilities used in these investigations are supported by the NSF-Sponsored MRSEC at UMass Amherst. This research used resources of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract DEAC02-06CH11357. A.C.J. and A.M.S. were supported by the Postgraduate Research Participation Program at the US Army Research Laboratory, administered by the Oak Ridge Institute of Science and Education through an interagency agreement between the US Department of Energy and Army Research Laboratory (Contract ORISE 1120-1120-99).