Mechanically improved sol-gel derived methacrylate-siloxane hybrid materials with urethane linkage

Ultraviolet (UV)-curable and highly condensed (>86%) methacrylate phenyl oligo-siloxane (MPO) was synthesized by non-hydrolytic sol–gel condensation reaction between methacrylate and phenyl silane precursor. The MPO resin was then cured by an UV-initiated free-radical polymerization to fabricate a transparent (>90% at 550 nm) methacrylate–siloxane hybrid material (methacrylate hybrimer). An urethane butanediol dimethacrylate (UBDM) monomer was synthesized as a cross-linker into the methacrylate hybrimer networks without micro-phase separation. The UBDM increased methacrylate conversion and mechanical properties due to the hydrogen bonding of the urethane linkage. The hardness, modulus, and strength were improved by UBDM insertion, the flexibility was even increased with 140% elongation, compared to neat MH. In addition, a storage modulus related to the thermo-mechanical properties was also enhanced by a denser cross-linkage with the urethane linkage.