Hybrid Silicon-Organic Methacrylate Monomers and Hyperbranched Polymers that Override the Ohnishi Parameter for Oxygen Plasma Etch Resistance

Efforts to develop next generation UV-curable optical materials for the encapsulation of an OLED, micro-LED, or quantum dot in electronic displays aim for a combination of ever-increasing oxygen plasma etch resistance, inkjet delivery, tailored refractive indices, and mechanical properties ranging from low (flexible) to high modulus. To this end, a range of low viscosity liquid hybrid silicon-organic methacrylates was synthesized and characterized, including mono- and difunctional carbosilanes, tri- and tetrafunctional carbosiloxane stars, and multifunctional hyperbranched polycarbosilane polymers. Ink formulations carrying silicon-containing methacrylates exhibited greater oxygen plasma etch resistance in comparison to silicon-free controls. Furthermore, it was demonstrated that etch resistance was proportional to weight percent elemental silicon content regardless of methacrylate functionality, molecular architecture, and molecular mass, and that this effect overrode the established empirical indicators of etch resistance for organics such as Ohnishi parameter and ring parameter. In addition, ink refractive indices could be tailored by controlling the phenyl level in the core composition of the star and hyperbranched methacrylates, and average methacrylate functionality, cross-link density, and glass-transition temperature could be controlled to enable either higher modulus layers or lower modulus flexible layers.