4(%3)3 - Ecole nationale supérieure de chimie de Montpellier

Figure – 1.27: Sulfur chemistry based synthesis of, a) Reversible cross-linked star polymers, b) Reduction andOxidation of SH/SS-Functionalized Star Polymers 154 .In a slight different approach 155 , a polymeric network was prepared from pentaerythritol tetra(3-mercaptopropionate) and triethyleneglycol divinyl ether along with a comonomer and instead of usingreduction – oxidation for reversible crosslinking, light was used an agent for trigerring the cleavage of theallyl sulfide linkages. This photoinduced cleavage led to plasticity, actuation, and equilibrium shapechanges without residual stress into the material.Although none of these works reported any data regarding self-healing property, the relativeease of reversibility (especially in case of photoinduced cleavage) of these systems exhibited pointstowards the capability of thiol chemistry for a robust self-healing system in applications like functionalcoatings. In one such instance, poly(n-butyl acrylate) grafted star polymers were prepared by chainextension ATRP from cross-linked cores comprised of poly(ethylene glycol diacrylate). These polymerswere further used as copolymerized with bis(2-methacryloyloxyethyl disulfide) (DSDMA), imparting32