ON THE UPTAKE OF AQUEOUS TRACER SOLUTIONS BY PRISTINE AND ION-IRRADIATED PEEK

The depth profiles of an aqueous tracer solution after its penetration into pristine and ion-irradiated poly(aryl ether-ether ketone) (PEEK) have been determined. Accompanying theoretical simulations have revea led that the penetration can be described by Case II diffusion with a depth dependent diffusion coefficient. The time dependence of tracer s olution uptake reveals that pristine PEEK is much less affected by swe lling than is the irradiated PEEK foil. Upon solvent uptake, ion-irrad iated PEEK readily transforms to its rubbery phase which binds around 1% of the tracer permanently. The diffusional mobility of the tracer s olution in the irradiated sample area is primarily governed by collisi onally induced defects which appear to exhibit some limited mobility t hemselves, For contrast, former findings by positron annihilation indi cated that the depth distribution of ion-induced free volume preferent ially follows the distribution of transferred electronic energy. We co nclude that the tracer uptake in PEEK is not only controlled by the fr ee volume but rather by the polymer morphology. This reveals a higher degree of complexity of the irradiated material than was anticipated b efore. (C) 1998 Elsevier Science B.V.