Self-Healable Dielectric Polydimethylsiloxane Composite Based on Zinc-Imidazole Coordination Bond

Abstract

Self-healing material has been intensively studied in the last decade due to its capability of improving materials’ lifetime and safety. Among the numerous proposed self-healing mechanisms, reversible metal-ligand coordination bond is considered as a strong candidate for a healing moiety because of its high tunability of mechanical properties based on the thermodynamic characteristics and kinetic parameters of metal ions or ligands. Furthermore, the dipolar nature of coordination bond can enhance the dielectric property of the material. Herein, zinc-imidazole coordination bond, having a fast ligand exchange rate in ambient condition, was employed as a healing moiety to synthesize room temperature self-healable polydimethylsiloxane (PDMS). Imidazole modified PDMS cross-linked by ligand and zinc ratio 4.5 (IMZ-PDMS-1100 L/Z 4.5) exhibited ultimate tensile strength (UT) of 60.73 kPa with ultimate extensibility (UE) of 211%. These mechanical properties could be adjusted by varying L/Z ratio and IMZ content. In comparison with previously reported metal-ligand based self-healing PDMS, IMZ-PDMS-1100 L/Z 4.5 showed faster healing rate that recovered 98% of UT and UE after 31 h healing and even faster healing rate was achieved with higher IMZ content. Moreover, cross-linked IMZ-PDMS displayed high dielectric constant of 8.30±0.74 at 1 MHz, which was 2.7 times higher than conventional PDMS.