Shape-memory effects of radiation crosslinked poly(ε-caprolactone)

Poly(epsilon-caprolactone) (PCL) with different molecular weight were crosslinked by gamma-radiation. The radiation crosslinking features were analyzed by Soxhlet extraction with toluene and the Charlesby-Pinner equation. The crosslinking degree is relative to molecular weight and radiation dose; the relation between sol fraction and dose follows the Charlesby-Pinner equation. All the samples were crystalline at room temperature, and the radiation crosslinking had a little effect on the crystallinity and the melting behavior of PCL. The shape-memory results indicated that only those specimens that had a sufficiently high crosslinking degree (gel content is higher than about 10%) were able to show the typical shape-memory effect, a large recoverable strain, and a high final recovery rate. The response temperature of the recovery effect (about 55degreesC) was related to the melting point of the samples. The PCL shape-memory polymer was characterized by its low recovery temperature and large recovery deformation that resulted from the aliphatic polyester chain of PCL. (C) 2003 Wiley Periodicals, Inc.