Design and fabrication of shape memory polyurethane network with rapid recoverable plastic deformation

Abstract

The flexible polymer substrate brings the possibility of recycling and reusing to the disposable electronics. Thus, it is necessary to explore a strategy to realize the structural reconfigurability and then improve the service life of polymers. Plastic deformation is one of key issues in failure of materials. Shape memory polymers (SMPs) with specific block structures are capable of remembering permanent shapes responding to various external stimuli. This excellent property is expected to contribute to the research of recoverable plastic deformation. In this work, a kind of plastic deformation-recovery shape memory polyurethane (PR-SMPU) was synthesized through bulk polymerization, where the semi-crystalline polycaprolactone (PCL) serves as soft segment and stimuli-responsive phase to achieve the recoverable character. By characterizing the mechanical properties and thermal stability, material with 40 wt% hard segment was selected, of which the breakage elongation ratio is 1126% at 20 °C and 1070% at 60 °C, the thermal stability can be guaranteed below 250 °C, and the plastic deformation can be recovered at 60 °C within 3 s. By analyzing the in-situ microstructural evolution in the constrained recovery after both elastic and plastic deformation, the mechanism of the recoverable plastic deformation of the proposed PR-SMPU were explored.