Semi-crystalline Biopol(TM) copolymers are biodegradable materials which are being intensively probed as suitable systems for embossed substrates in tissue regeneration applications. However, it has been shown that an embrittlement process occurs on storage at room temperature which places restrictions as to their application possibilities. In order to study this process we have made use of Biopol(TM) systems which have aged for 3 years since extrusion as thin films, and subsequently rejuvenated at elevated temperatures. Utilising varying techniques we have attempted to shed light on the mechanisms responsible for the rejuvenation, with particular emphasis on the observed dielectric properties. We highlight the possibility of on-going secondary crystallisation on ageing and attempt to rationalise the rejuvenation in terms of release of amorphous material from the rigid amorphous phase of semi-crystalline systems. (C) 2004 Kluwer Academic Publishers.