Citric acid-induced room temperature self-healing polysiloxane elastomers with tunable mechanical properties and untraditional AIE fluorescence

Polysiloxane plays an irreplaceable role in aviation, automobile, flexible electronic devices, electrical engineering, etc. However, the poor mechanical strength makes it prone to damage during the working process. Therefore, it is of great significance to develop self-healing polysiloxane material. In this work, we prepared a silicon elastomer (CA-PDMS) by introducing citric acid (CA) and urea-group into the polydimethylsiloxane polymer chains, which featured a dynamic cross-linking network of multiple types of hydrogen bond synergies. The elastomer was mechanically tunable by adjustment of the ratio of the hydrogen bonds between the two parts. With an increase in the CA ratio, the elastomers showed a trend from “hard” to “soft”. The maximum elongation at break achieved was 1076.3%, revealing excellent stretchability. Due to the dynamic reversibility of hydrogen bonds, CA-PDMS showed conspicuous self-healing capability and CA had a positive impact on self-healing. Self-healing efficiency was >95% at 60 °C, while the self-healing efficiency reached 81.4% at room temperature. Compared with PDMS-0 without CA, the improvement was respectively about one and seven times. What's more, CA is commonly prepared as carbon quantum dots, compounding with polymer to obtain luminescent materials. Unlike previous research, this study introduced CA into the PDMS polymer chains through polymerization, generating untraditional light-emitting amide groups to achieve luminescence. As far as we know, this is the first time that CA has been reported to improve self-healing and ductility and realize AIE emission by co-polymerization with PDMS.