On the role of penetrant structure in diffusion in structured polymers

Marked differences between the diffusional behaviour of linear and non-linear penetrant molecules in structured polymers exist, which remain hitherto unexplained. The existing theories of transport in polymers have been re-examined with a view to explain such differences. Direct and indirect experimental evidence has been analysed to support the view-point that linear molecules diffuse by a segmental motion. A diagnostic method in the context of a modified Maxwell model has been proposed to differentiate between different diffusive phenomena. The role of co-operative segmental motion for the polymer matrix has been quantitatively examined. Possible technological implications of the findings of the work have been elaborated on.