Blends of S-PAEK with Inert Polymers

Another class of chemically exceptionally stable polymers are the poly(para-phenylene)s. In addition, they are stiff, rod-Uke polymers. This feature usually tends to cause insolubihty of polymers, which is an attractive approach rod-like polymers can be expected to be insoluble in water at much higher lEC values than polymers consisting of flexible chains, such as poly(arylene ether)s. Since proton conductivity depends on lEC, such polymers have the potential to form membranes with high conductivity at relatively low degrees of swelling and good dimensional and mechanical stability. 

The poly(para-phenylenes)s can be considered rigid rod polymers, which distinguishes them from aU other types of polymers typically used for proton conducting membranes, possibly with the exception of certain polyimides. A striking consequence of the rigid rod structure is the fact that the poly(para- 

Probably because of limited molar mass, the brittleness of these poly(para-phenylene)s can be compensated by incorporating them as sulfonated segments into block copolymers with poly(aryl ether sulfone)s (78). As for the poly(aryl ether ketone) block copolymers, water uptake is reduced while relatively high conductivity (considering the lEC) is maintained [78]. 

Another method [77] for the synthesis of poly(para-phenylene)s utihzes a reaction which was already successfully used by Stille [83-85] in the 1960s Diels-Alder reaction (Fig. 15). 

A third pathway to soluble poly(parfl-phenylene)s is Ulhnann coupUng of sulfonated dibromo biphenyl monomers [80] (Fig. 16). 

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