Rheology, dynamics, and mechanisms of self-healing of polydimethylsiloxane dual-linked by ureido and dynamic imine bonds.

For the self-healing polymer, the recovery of mechanical properties and self-healing mechanisms are significantly affected by the time and temperature dependences of physical and chemical bonding dynamics, or by a synergistic combination of the two. In this work, the self-healing dynamics of chains consisting of short polydimethylsiloxane (PDMS) blocks joined together at their ends through both hydrogen-bond-forming ureido and dynamic imine linkages are systematically investigated by shear and extensional rheology, in situ Fourier transfer infrared spectra (FTIR), and self-healing time of severed samples. Using synthesized polymers with different ratios of ureido and imine linkages and measuring rheology and dynamics of the self-healing process over a range of temperatures, it is shown that the self-healing time is comparable to characteristic relaxation time (the inverse of the cross-over frequency of G' and G″ near the terminal zone).