UV-Cleavable Polyrotaxane Cross-Linker for Modulating Mechanical Strength of Photocurable Resin Plastics

A UV-cleavable supramolecular cross-linker was designed to effectively control the mechanical strength of photocurable resin plastics. The resin monomer-soluble polyrotaxane (PRX) cross-linker was synthesized by introducing a hydrophobic n-butyl group and a cross-linkable methacrylate group in α-cyclodextrin threading to a polyethylene glycol containing UV-cleavable end groups. The UV-cleavable PRX cross-linker was completely dissolved in 2-hydroxyethytl methacrylate (HEMA) and camphorquinone, representative photocurable resin components. The dumbbell-like stiff resin plastic was prepared by irradiating the mixture with 450 nm blue light. The stiffened resin plastic maintained its ultimate tensile strength (UTS) under visible light irradiation. However, the UTS of the resin plastic was remarkably decreased to 40% of the original value once the plastic was exposed to 254 nm UV light. This indicates that the suggested UV-cleavable PRX cross-linker is effective in modulating the mechanical strength of photocurable resin plastics.