Self-Healing Polymer-based Nanocomposites using the Diels-Alder-reaction: Studies on the Influence of Composition on Self-Healing Properties

Abstract

SiO2-nanoparticle-polymer–interfaces were tested according to their suitability as a DA - reversible crosslinking site. The role of the chemical composition of the polymer matrix was shown. Cuts of several millimeters could be healed within the siloxane-based nanocomposite, after reconnection of cut surfaces with the help of chloroform, by the DA reaction. The limit of interface-reactivity was investigated in a cofunctionalization study. Therefore, FexOy nanoparticles were functionalized with a monolayer DA-alkyl phosphonic acids. A drastic drop in conversion was recorded, when the attacking reagents were dodecyl derivatives of maleimide and furan instead of maleimide/methylfuran. This result indicates, that due to the sterical situation created by the attacking reagent on the surface only a minimal conversion with polymer chains is possible Therefore, diene and dienophile were distributed statistically within the matrix, instead of being located cumulative at the particle surface. Linear one-component polymers, consisting of diene, dienophile and one additional hydrogen bonding motive were synthesized using controlled radical polymerization techniques. Urea-group bearing spherosilicates were synthesized in high yields. By blending these both components, a hybrid material with double intrinsically reversible networks was received. The H bonds reconnect cut interfaces at 30°C, whereafter cuts in the mm-scale could be healed by the DA reaction.