Functionalization by Chemical Grafting Reactions

A promising alternative to the direct functionalization (sulfonation phospho-nation) of high performance polymers is offered by the chemical grafting 

Since the polymers to be activated need to have at least one acidic proton in the main chain and must be soluble in suitable solvents, the number of polymers which can be modified by this particular method is limited. So far only the modification of poly(arylene ether sulfone)s and polybenzimidazoles as suitable materials for fuel cell membranes has been reported in the literature [4,5,32,102,136-146,148-151]. The attempt to lithiate poly(ether sulfone) under homogeneous conditions failed so far, due to poor solubility and the alternating electron-donating and electron-withdrawing linkages present in poly(ether sulfone), which result in an overall unfavorable balance in the polymer chain. 

Besides the covalent crosslinking, Kerres et al. investigated the properties of fuel cell membranes of ionicaUy crosslinked polysulfonic adds. This type of crosslinking was achieved by blending sulfonated poly(arylene ether sul-fone)s and poly(arylene ether ketone)s with basic polymers, such as polybenzimidazole, poly(ethylene imine), poly(vinyl pyridine), or amino functional- 

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