Synergetic Chemical and Physical Programming for Reversible Shape Memory Effect in a Dynamic Covalent Network with Two Crystalline Phases

Abstract

A recently emerged reversible shape memory effect greatly extends the capability of shape memory polymers and their practical potential. Physical confinement and chemical fixation are individually known to be effective in introducing network anisotropy essential for reversible shape memory. Herein, we demonstrate that synergetic combination of these two mechanisms effectively diversifies the shape-shifting behavior. Specifically, we introduce a transesterification catalyst into a network containing two crystalline phases: poly(ε-caprolactone) (PCL) and poly(ω-pentadecalactone) (PPDL). The reversible shape memory behavior of the resulting system can be programmed via the physical confinement by the PPDL phase and the chemical plasticity by the dynamic ester exchange. We illustrate that the two programming mechanisms can operate in a noninterfering way that allows achieving a synergetic benefit, notably realizing a zero-set reversible shape memory behavior. Our study points to a direction in diversifying the behaviors of reversible shape memory polymers and expands the scope for potential engineering devices.