BDSA/NTDA/ODA

Fig. 20 Ionic conductivity versus ionic block length for BDSA/NTDA/ODA copolymers (Scheme 3k) with xjy = 30 70...

In another example of the importance of polymer microstructure, the variation of proton conductivity of BDSA/NTDA/ODA copolymers (Scheme 3k) with ionic sequence length is shown in Fig. 20 [143], where an ionic length of 1 represents a statistical copolymer. Water uptake for copolymers with different ionic block lengths (block lengths in brackets) are (1) 39.3%, (3) 40.6%, (5) 44.3%, and (9) 69.3%. Corresponding A ([H20]/[S03H]) values are 17, 18, 20, and 30. Proton conductivity does not linearly relate to water uptake in the polymers, and this may reflect a secondary influence of proton concentration in the hydrated membranes. 

Sulfonated polyimides (sPI) are another type of ionomers that have been prepared [5] by copolymerization of 4,4 -diamino-biphenyl 2,2 -disulphonic acid (BDSA), 4,4 -oxydianiline (ODA), and naphtalenic or phthalic anhydrides. Polyimide structures based on six-membered rings derived from naphtalenics anhydrides, such as 1,4,5,8-naphtalene tetracarboxylic dianhydride (NTDA), shown in Fig. 6.8, are more hydrolitically stable than the five-membered rings basedoxy-diphthalic anhydrides (ODPA). 

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