Siloxanic proton-conducting membranes

D-HION-APPE proton conducting materials are presented as an important development to replace the ubiquitous and costly perfluorinated ionomers currently in use. These materials can be synthesized by the copolymerization of metal alkoxides and organic-substituted silicon alkoxides or suitable oligomers. In particular, two new siloxanic proton-conducting membranes are described (Di Noto and Vittadello, 2005 Di Noto et al, 2005) ... 

DI NOTO V, vrrTADELLo M (2005), Two new siloxanic proton-conducting membranes Part I. Synthesis and structural characterization , Electrochim Acta, 50, 3998-4006. 

Fig. 5.22 Proton-conducting membrane based on benzyl sulphonic acid siloxane.

Crosslinked sulfonated poly(imide-siloxane) can be obtained by the radical grafting onto the silylmethyl group of poly(dimethylsiloxane) [59]. Large, well-connected hydrophilic domains have been detected by transmission electron microscopy that are responsible for the high proton conductivity of the membrane. The unique phase separated morphology of the membrane is responsible for the outstanding hydrolytic stability. 

Semi-interpenetrating polymer network membranes based on sulfonated polyimide-siloxane and epoxy polymers have been prepared [61]. The membranes show desirable mechanical properties and thermal stabilities, with proton conductivities superior to those of Nation 117 at 80 °C. 

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