Polymerisation of Ionic Monomers by Step Growth

1 Ionomers Containing Hexafluoro-Isopropylidene or land Polar Functions 

The most studied commercial polymer in the chemical modification, Udel polyethersulfones are based on bis-phenol A, in which the electron-donating isopropylidene moiety increases the electronic density of the whole phenoxy sites and, in particular, increases the ether basicity. This may favour chain breaking during the sulfona-tion step [29,32] the former may favour free-radical attacks on the aromatic rings. 

Moving from bis-phenol A (BPA) to its fluorinated form (BHFPA) (by replacing iso-propylidene by hexafluoro- isopropylidene), is one of the ideas to overcome both drawbacks. In addition, due to the perfluorinated moiety of BHFPA, a decrease in the hydrophilic character of the related ionomer can be expected. Kim et al. [48] reported the effects induced by BHFPA and non-ionic polar monomers in 

In spite of the decrease in the basicity of BHFPA that should lower their reactivity in nucleophilic aromatic substitution, the ionomer synthesis was successful. Surprisingly, the water uptake dependence of the ionomers on lEC was found to be almost unaffected by the presence of the BHFPA repeat unit. This result, in agreement 

While the conductivity decrease is a shortcoming of polar groups, their incorporation may lead to advantages in terms of (i) mechanical performance, (ii) decrease in membrane-electrode interfacial resistance, and (iii) decrease in methanol crossover, which is an asset for an implementation in direct methanol fuel cells (DMFC), provided high selectivity (ratio of proton conductivity to methanol permeability) is retained [52]. While comparing the effects of polar groups, it appears that phenylphosphine incorporation. 

---

Polymerisation of ionic monomers by step- growth polymerisation... 

---