Self-healing nanocomposites from silica - polymer core - shell nanoparticles

A copolymer containing butyl methacrylate in a 10-fold excess and furan-protected maleimidopropyl methacrylate was synthesized via atom transfer radical polymerization (ATRP). Maleimide functionalities served as dienophiles for reversible crosslinking by Diels - Alder (DA) reactions. As counterpart to the linear polymer, silica - polymer core - shell nanoparticles with grafted furfuryl groups were prepared by surface-initiated ATRP. Rheological measurements during the DA reaction at 80 degrees C showed an increase in storage modulus due to crosslinking within the nanocomposite. DSC allowed the detection of the endothermic retro-DA reaction above 120 degrees C, which provided the possibility to self-heal scratches. Repeated curing/de-crosslinking was detected using UV-visible spectroscopy and revealed the reproducibility of the thermoreversible crosslinking reaction, which is a prerequisite for the self-healing mechanism. Finally, the scratch-healing abilities of the material were verified on composite films. (c) 2013 Society of Chemical Industry