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

Abstract

Self-healing material has been intensively studied in 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 due to their broad thermodynamics and kinetic parameters. Furthermore, 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 healing moiety to synthesize room temperature self-healable polydimethylsiloxane (PDMS). Imidazole modified acrylate (IMZa) was prepared and imidazole modified PDMS (IMZ-PDMS) was synthesized by grafting IMZa onto PDMS backbone. IMZ-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 211.46 %. 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 8.78 ± 0.42 at 1 MHz, which was 2.9 times higher than conventional PDMS.