SELF-HEALING SUPRAMOLECULAR POLYMER NANOCOMPOSITES

Polyborosiloxanes (PBSs) are viscoelastic, transparent, colourless, self-healable polymer matrices, synthesized by reacting linear polydimethylsiloxanes (PDMSs) with boric acid (BA) above 150°C. BA takes part not only in cleaving the PDMS chains, but also contributes boronic-acid like moieties to the cleaved chain ends, which provide supramolecular self-healing capabilities. PBSs can be regarded as supramolecular elastomers, owing to the reversible cross links formed by the abundant hydroxyl groups. Therefore they are able to recover both the microscopic and macroscopic fractures intrinsically via hydrogen-bonds. Additionally, a glass transition temperature (Tg) as low as-90°C ensures chain mobility to PBSs molecules to heal cracks autonomously without extra heat supply. Compared to traditional carbon-based polymeric materials, PBSs provide a higher resistance to heat and light owing to the siloxane backbone. Upon increasing the degree of modification, PBSs get stronger on the one hand. However, PBSs also become less adhesive and start suffering from brittle fracture. Interestingly, the addition of nano-clay (Cloisite 30B