Polyfluorenes Bearing <i>N</i>,<i>N</i>-Dimethylpiperidinium Cations on Short Spacers for Durable Anion Exchange Membranes

Alicyclic quaternary ammonium cations having all the β-protons in a strain-free ring structure are general highly base-resistant and thus very attractive to employ for anion exchange membrane (AEM) applications. However, tethering such as N,N-dimethylpiperidinium (DMP) polymer backbones without introducing any weak links is quite challenging. In present study, we have attached pairs of piperidine rings their 4-position fluorene 2,7-diphenylfluorene via methylene bridges using straightforward SN2 reactions. These fluorenes were subsequently utilized monomers polyhydroxyalkylations prepare poly(fluorene alkylene)s with different contents groups. AEMs cast after quaternizing groups introduce DMP spirocyclic 6-azonia-spiro-[5,5]undecane-6-ium (ASU) cations, respectively. The reached high hydroxide ion conductivities, 100–156 mS cm–1 at 80 °C, capacity range 1.8–2.4 mequiv g–1. X-ray scattering showed ionomer peaks indicating ionic clustering characteristic distance d = 2.0–2.9 nm depending on capacity. displayed thermal stability, up ∼250 1H NMR data indicated no degradation storage 5 M aq NaOH during 168 h 90 °C. started under severe conditions (10 M, °C) ∼75% total loss assigned Hofmann β-elimination. overall results show that fluorene-based carrying ASU display an combination phase separation, chemical conductivity, making them viable alternatives use alkaline fuel cells water electrolyzers..