ABSTRACT Small molecules transport in polymeric systems is of great importance in many technological applications of polymer based manufacts. Membrane separation systems, polymer based drug delivery devices, solvent absorption media, barrier structures for food packaging, durability of polymer based composite materials are some of many applications in which mass transport plays a major role. In fact, this phenomenon has to be deeply understood in order to properly design polymer based systems to be used in the mentioned fields. In this paper the influence of polymer physical state and morphology on transport properties is addressed. Crystallinity level, crystal morphology, degree of orientation and polymer chemical structure are all factors to be taken into account when a polymeric material has to be properly selected for technological applications where mass transport properties are of primary interest. In this paper we analyze two specific examples in which the relationship between mass transport properties and polymer structure in semicrystalline systems is exploited. In particular the effect of film thickness on oxygen sorption and transport in dry and water saturated Kapton® polyimide and effects of polymer micro- and macro- structure on gas transport properties of polyethylene based ionomers used in food packaging applications will be presented. The former class of materials is used in the field of protection of electronic devices while the latter is widely applied in food packaging.
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