Thermoreversibly cross-linked poly-ε-caprolactones for the elaboration of shape memory materials

This contribution aims at reporting a new concept for the preparation of well defined and recyclable PCL- based reversibly cross-linked shape memory polymer by the formation of reversible carbon-carbon bonds. For this purpose, commercially-available star-shaped PCL precursors were selected and selectively modified at their chain ends either by a diene (furan) or a dienophile (maleimide). PCL-based shape memory materials were prepared by mixing a stoichiometric amount of diene-bearing and maleimide-bearing PCLs at a temperature which favors cycloreversion. The polymer blend is then cured at 65°C (slightly above PCL melting temperature), with the purpose to increase chains mobility and improve the formation of the adducts. The Diels-Alder kinetics has been followed by Raman spectroscopy and the PCL cross-linking was evidenced by both swelling experiments and rheological measurements. The obtained cross-linked PCL was characterized by shape memory properties with excellent fixity and recovery, as determined by cyclic tensile thermomechanical analysis.