Diffusion of14CO2 in Polyurethanes

Summary Diffusion coefficients and their temperature coefficients were obtained on a series of four polyurethanes believed to differ mainly in their molecular chain stiffness, and on one partially crystalline polyurethane of high molecular symmetry having flexible chains. The diffusion coefficients of CO₂ in these materials and their temperature dependence are f ound to be much lower than those of many other typical organic polymers, notably rubbers. The data are interpreted in terms of theH-bonds formed between neighbouring polymer chains which are thought to make for regions of high packing efficiency, interrupted at irregular intervals by more open regions of small size. The effect of molecular chain flexibility appears to be smaller than the influence of theH-bonding.