Evaluation of novel urethane dimethacrylates as crosslinkers for the development of fracture tough dental materials containing a poly(ε-caprolactone)-polydimethylsiloxane-poly(ε-caprolactone) triblock copolymer

Abstract

Photocuring 3D printing of materials exhibiting high fracture toughness and excellent mechanical properties (flexural strength/modulus) is challenging. Nowadays, most of the photocurable 3D printing resins are based on a mixture of multifunctional (meth)acrylates and provide therefore brittle materials. This article describes further developments of a toughening strategy based on the incorporation of block copolymers in low crosslink density methacrylate-based materials. Six dimethacrylates bearing a bisphenol A core and urethane groups are successfully synthesized. Various spacers between the bisphenol A core and the methacrylate groups are selected. Each monomer is combined with (octahydro-4,7-methano-1H-indenyl)methyl acrylate as a monofunctional monomer and a poly(ε-caprolactone)-polydimethylsiloxane-poly(ε-caprolactone) triblock copolymer is added as toughener. It is shown that the addition of the triblock copolymer results for all mixtures in a strong increase of the fracture toughness. Moreover, the higher the amount of monofunctional monomer, the stronger the increase. The nature of the urethane dimethacrylate is found to have a significant influence on the fracture toughness, flexural strength, and flexural modulus of cured materials. Two of the synthesized dimethacrylates are identified as promising candidates for the development of fracture-tough photocuring 3D printing materials.