Mechanical properties of methacrylate siloxane hybrimer according to molecular structure

Abstract

Recently, a flexible display has been substituted a flat panel display on electronic device market. For driving the flexible display, all devices in display should be also flexible

substrates, conducting electrodes, batteries, etc. Nowadays, fixed-curved displays, which cannot deform the bending radius, are commercialized in the display market. Other devices except hard coating are studied and manufactured with flexibility, but the hard coating is hard to substitute an existing cover glass, which structure is a 3-dimensional siloxane network and has high optical and mechanical property. However, the thin glass has weakness of brittleness, so new materials for hard coating should be developed for traditional meaning of flexible display. So lots of flexible materials have been studied, but the incompatibility of mechanical property and flexibility makes the development be slow. In this study, organic-inorganic hybrid material (Hybrimer) with methacrylate organo-trimethoxy silane, which is inspired by glass’ 3-dimensional siloxane network, is fabricated by simple sol-gel process and free-radical polymerization. We synthesize random-structure and ladder-structure methacrylate oligo-siloxane at first, their optical and mechanical properties are investigated. The ordered ladder-like structure hybrimer has superior optical and mechanical properties, but it is more brittle than random-structure hybrimer. We choose a urethane dimethacrylate monomer for cross-linkage within methacrylate hybrimer, because the urethane is well known mechanical properties with high elongation and scratch resistance. The urethane dimethacrylate is synthesized in this study, and the new hybrimer is fabricated from ladder-structure oligo-siloxane and urethane dimethacrylate. Its optical and mechanical properties are investigated, compared to pure ladder-structure methacrylate hybrimer (LMH), and LMH with alkyl linkage and ethylene glycol, which are comparison groups and have similar length with urethane dimethacrylate. Hydrogen bonding in urethane enhances methacrylate conversion, then the mechanical properties like flexural modulus and strength are improved, and the flexibility is also enhanced at the same time.