(346i) Diffusion in Pebax Block Copolymers: Effects of Diffusant Mass and Polymer Composition

The rate at which small molecules diffuse through polyether-b-polyamide (PEBAX) copolymers is crucially important to their applications as controlled release media and gas separation membranes. PEBAX may also be blended with additives and used in medical devices, in which case accurate predictions of how fast those additives are released into the human body will serve the needs of public health. These uses have motivated us to experimentally measure a set of representative diffusion (D) and partition (K) coefficients over a wide range of diffusant masses (MW, ca. 50 â?? 550 Da) and polyether contents (0 â?? 84 mol. %) via a variety of gravimetric and spectroscopic sorption techniques. Here we will show that log(D) vs. log(MW) is linearly proportional with a slope of -4.7 within PEBAX 4033. The effect of polyether content on D and K can be well-accounted for by the effective medium theory of Sax and Ottino for transport in heterogeneous materials. These results broadly define upper limits on patient exposure to device additives, which will be useful in subsequently gauging the potential risks of being exposed to additives.