Design of a mechanically strong and highly stretchable thermoplastic silicone elastomer based on coulombic interactions

Abstract

The combination of mechanical properties, self-healing capability and recyclability is practically considered for silicone elastomers. Here, thermoplastic silicone elastomers (TPSEs) were prepared via cross-linking solely by coulombic interactions between carboxylic acid groups on the polydimethylsiloxane (PDMS) side chains and commercially available zinc oxide (ZnO). To obtain an ideally desirable combination of great mechanical strength, elasticity and self-healing properties, three linear vinyl-containing PDMS samples were synthesized via a cyclic trimeric phosphazene base (CTPB) catalyzed ring-opening polymerization and then used as a precursor to afford carboxylic acid functionalized PDMS (PDMS-g-COOH) via an efficient thiol–ene click reaction. The final TPSEs were formed by simple mixing of PDMS-g-COOH with ZnO. The mechanical properties and self-healing abilities of dynamic salt-bonding networks were tuned by varying the molecular weights of PDMS precursors and the molar ratio of COOH/ZnO, characterized by dynamic mechanical analysis (DMA) and tensile and rheological measurements. The obtained PDMS-g-COOH/ZnO composites exhibited an excellent mechanical strength of >5 MPa, good elasticity up to 1300% of the original length and fast self-healing efficiency of 83.5% at 80 °C for 4 h. This simple and universal approach provided new insights into next-generation high-performance TPSEs.