Aliphatic Anion Exchange Ionomers with Long Spacers and No Ether Links by Ziegler-Natta Polymerization: Properties and Alkaline Stability

In this work we report the synthesis of poly(vinylbenzylchloride-co-hexene) copolymer grafted with N,N-dimethylhexylammonium groups to study the effect of an aliphatic backbone without ether linkage on the ionomer properties. The copolymerization was achieved by the Ziegler-Natta method, employing the complex ZrCl4 (THF)(2) as a catalyst. A certain degree of crosslinking with N,N,N ',N '-tetramethylethylenediamine (TEMED) was introduced with the aim of avoiding excessive swelling in water. The resulting anion exchange polymers were characterized by H-1-NMR, FTIR, TGA, and ion exchange capacity (IEC) measurements. The ionomers showed good alkaline stability; after 72 h of treatment in 2 M KOH at 80 degrees C the remaining IEC of 76% confirms that ionomers without ether bonds are less sensitive to a S(N)2 attack and suggests the possibility of their use as a binder in a fuel cell electrode formulation. The ionomers were also blended with polyvinyl alcohol (PVA) and crosslinked with glutaraldehyde. The water uptake of the blend membranes was around 110% at 25 degrees C. The ionic conductivity at 25 degrees C in the OH- form was 29.5 mS/cm.

Automated summary

In this study, the synthesis of a copolymer of poly(vinylbenzylchloride-co-hexene) grafting N,N-dimethylhexylammonium groups was reported to investigate the effect of an aliphatic backbone without ether linkage on the ionomer properties. The results showed that ionomers without ether bonds exhibited good alkaline stability and lower sensitivity, making them potential binders in fuel cell electrode formulations.