Structure and Properties of Sulfonated Polyimide

These values seem signifieantly different, while they are very elose when expressed as equivalent volume (524 and 550 cm /equiv., respeetively). However, the polymer matrix density is not easy to determine experimentally eompared with the dry weight and the equivalent volume is never used. 

2 Physical Structure and Morphology It is commonly accepted that the membrane microstructure has a large impact on the transport properties and should 

In the SAXS data obtained for phthalic block copolymers where the ionomer peak is well defined, the peak position was found to be proportional to the number of repeat 

More recently, another intermediate timescale was explored by NMR relaxom-etry [102]. The spin-lattice relaxation times of water molecules were determined in the range of 20 ns to 20 ps by varying the magnetic field frequency from 10 kHz to 20 MHz and depending on the water content. This technique is well suited for the study of ionomer membranes because of its extreme sensitivity to water-polymer interactions, but it requires a structural and dynamic model to extract characteristic features. The effect of confinement is predominant in polyimides even at high water content (algebraic law with a slope of —0.5 characteristic of porous materials), whereas the diffusion quickly reaches a bulk behavior in Nafion (a plateau is observed at low magnetic fields). 

A surprising result also arises from the comparison of the water uptake values obtained after membrane equUibration in pure water and in a saturated vapor 

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