Molecular Design for Reversible Deformation beyond Elastic Recovery

In this study, we propose a molecular design strategy to reversibly control stress whitening beyond conventional elastic recovery. A furan-based polyester elastomer was synthesized using dimethyl 2,5-furandicarboxylate (DMFD), neopentyl glycol (NPG), and poly(trimethylene ether) glycol (PO3G). The synthesized copolyester exhibited excellent mechanical properties and recovery behavior. In particular, PNF-7G showed a Young’s modulus of 444.7 MPa and an elongation at break of 574.8%. Stable recovery was observed even after stress whitening during a 10-cycle tensile test, and the recovery ratio remained above 90% in the post-whitening deformation region.
To investigate the structural origin of whitening and recovery, XRD, Raman spectroscopy, and solid-state NMR analyses were conducted. The results showed that alignment and packing changes of FDCA-based hard segments were involved in whitening and recovery, leading to a new structural state after recovery. Furthermore, two-dimensional correlation spectroscopy (2DCOS) revealed sequential molecular rearrangement during the whitening and recovery processes.
Therefore, this study confirms that the nonlinear structural characteristics of FDCA provide a structural basis for rearrangement without permanent damage. These findings suggest a molecular design strategy for materials capable of recovery even after stress whitening and demonstrate their potential as sustainable materials with high resilience under repeated deformation.