Gas transport properties of segmented polyurethanes varying in the kind of soft segments

The gas transport behaviour of the series of structurally different polyurethanes (PU) was studied in detail. The polymers investigated were synthesised from various macrodiols, including hydroxy terminated polyethers, polyesters and polydienes, 2,4-diisocyanate (2,4-TDI) and a low molecular weight diol as a chain extender. The structural variations introduced were manifested by the differences in the Tg and density values of the resulting materials and by their various transport properties. Membranes obtained from PUs with more polar or shorter macrodiol segments, or with an addition of a chain extender were seen to exhibit the lower permeability. The diffusivity and solubility of oxygen and nitrogen in PUs were found to correlate with the glass transition temperature of macrodiol segments. The selectivity results demonstrate that PUs studied are more selective than conventional PUs reported in literature. Unexpectedly, some of the most selective PUs exhibited also the highest permeability.