Synthesis of Multiwalled Carbon Nanotube-Reinforced Polyborosiloxane Nanocomposites with Mechanically Adaptive and Self-Healing Capabilities for Flexible Conductors

Intrinsic self-healing polyborosiloxane (PBS) and its multi-walled carbon nanotube (MWCNT)-reinforced nanocomposites were synthesized from hydroxyl terminated poly(dimethylsiloxane) (PDMS) and boric acid at room temperature. The formation of Si-O-B moiety in PBS was confirmed by Fourier transform infrared spectroscopy. PBS and its MWCNT-reinforced nanocomposites were found possessing water or methanol activated mechanically adaptive behaviors; the compressive modulus decreased substantially when exposed to water or methanol vapor and recovered their high value after the stimulus was removed. The compressive modulus was reduced by 76%, 86%, 90% and 83% for neat PBS and its nanocomposites containing 3.0 wt.%, 6.2 wt.% and 13.3 wt.% MWCNTs, respectively, in water vapor, and the modulus reduction activated by methanol vapor was greater than by water vapor. MWCNTs at higher contents acted as a continuous electrical channel in PBS offering electrical conductivity, which was up to 1.21 S/cm for the nanocomposite containing 13.3 wt.% MWCNTs. The MWCNT-reinforced PBS nanocomposites also showed excellent mechanically and electrically self-healing properties, moldability and adhesion to PDMS elastomer substrate. These properties enabled a straightforward fabrication of self-repairing MWCNT/PBS electronic circuits on PDMS elastomer substrates.