Reversible cross-linking of polysiloxanes by cooperative hydrogen bonds

摘要

Polysiloxanes (PDMS) and other polymers are used as sheathing materials in the cable industry. In order to achieve satisfactory mechanical and thermo-mechanical properties for this application, these polymers are chemically cross-linked during expensive and time-consuming extrusion or post-extrusion processes. The purpose of the present work is to replace classical chemical cross-linking by non-covalent but strong interactions. Supramolecular polymers, which are small molecules able to self-assemble into polymer-like structures, could enhanced the mechanical properties of polymers because their association is reversible and spontaneous. Indeed, these molecules may simplify the overall cross-linking process, leading to chapter and recyclable materials. Several groups have already shown that hydrogen bonds are particularly interesting for this application thanks to their relative strength compare to that of other weak interactions. Recently, we have focused on bis-ureas (Figure 1), which may self-assemble into rigid wires through four strong cooperative hydrogen bonds and exhibit very impressive rheological properties in apolar solvents. These molecules, grafted on a polymer, should act as multiple and very strong reversible cross-linking points (Figure 2). Moreover, their easy and cheap synthesis is compatible with industrial applications.