Highly transparent and resilient urethane-methacrylate siloxane composite for hard, yet stretchable protective coating

Although foldable electronic devices have been commercially available for some time now, flexible protective coating with sufficient reliability is yet to be achieved. The integration of polyurethane acrylate and an organic-inorganic (O-I) siloxane hybrid is proposed in this study as a promising protective coating, where both high strength and stretchability could be achieved to allow for the needed reliability for foldable electronics. In this work, a urethane-methacrylate siloxane hybrid (U-MSH) composite was fabricated by a physical blending of methacrylate-functionalized oligosiloxane and acrylate terminated urethane prepolymer followed by curing. The U-MSH composite demonstrates excellent performance in terms of optical (e.g., transmittance, Abbe number, UV stability) and mechanical properties (e.g., resilience under compression, tension, and scratch). These outstanding properties can be attributed to the synergetic effect of the combined polyurethane acrylate and O-I siloxane hybrid. Excellent reliability of U-MSH coating film is successfully demonstrated using an outward-bending test, suggesting that U-MSH has great potential as a protective material for flexible electronics. •UV-curable acrylate-terminated urethane prepolymer was synthesized via urethane formation reaction.•Methacrylate-functionalized siloxane resin was synthesized via sol-gel reaction.•Highly transparent urethane-methacrylate siloxane hybrid composite (U-MSH) material was successfully fabricated.•U-MSH exhibited the excellent performance in tensile, compression and scratch tests.•U-MSH coating film is demonstrated without shrinkage/cracking and endured outward-bending test.