Tailor‐Made Functional Polymethacrylates with Dual Characteristics of Self‐Healing and Shape‐Memory Based on Dynamic Covalent Chemistry. Issue 6 (20th May 2020) - Mondal, Prantik
Abstract: New shape memory polymers with self‐healing behavior are obtained by thermoreversible Diels–Alder (DA) cross‐linking of a furfuryl group‐containing star‐block copolymer with 1, 1′‐(methylenedi‐4, 1‐phenylene)bismaleimide. The star‐block copolymer consisting of a 3‐arm polycaprolactone (PCL) core and a polyfurfuryl methacrylate shell is synthesized by reversible addition–fragmentation chain transfer (RAFT) polymerization. For this, a 3‐arm macro‐RAFT agent based on PCL is converted with an appropriate amount of furfuryl methacrylate in the presence of a radical initiator. Films of the DA network are partly insoluble at ambient temperatures. After annealing at 120 °C the films become completely soluble because of the progressing retro‐DA reaction. Evaporation of the solvent and subsequent annealing at 60 °C restores the original insoluble state of the material. By means of a scratch test and tensile tests on cut and subsequently mended samples it is shown that the retro‐DA reaction facilitates self‐healing. Additionally, the films show pronounced shape memory effects with reasonable shape recovery and fixity ratios, which are attributed to the melting and crystallization of the PCL phase. Abstract : 3‐Arm star‐block copolymers with furfuryl groups in the shell are obtained by reversible addition‐fragmentation chain transfer (RAFT) polymerization of furfuryl methacrylate initiated by a macro‐RAFT agent based on a 3‐arm polycaprolactone. After cross‐linking of the polymer by thermo‐reversible Diels‐Alder cycloaddition with a bismaleimide a material with dynamic chemical bonds is obtained that shows pronounced shape memory and self‐healing behavior.