High-refractive-index ethylene/cyclic olefin/octene terpolymers with high optical transparency

Abstract

Cyclic olefin copolymer is one of the most promising optical materials, but suffers from the issue of relatively low refractive index. The incorporation of 1-olefin into the polymer chain markedly enhanced its flexibility and solubility, and the elongation at break showed a corresponding rise, although the tensile strength underwent a decrease. In this contribution, the flexible 1-octene as the third comonomer was introduced to conduct the terpolymerization with ethylene and cyclic olefins by using the zirconocene catalyst under the activation of methylaluminoxane. The microstructures of the resultant terpolymers were characterized, and the effect of the incorporated 1-octene was determined by analyzing the optical, thermal and mechanical properties of the terpolymers. By introducing 1-octene, the glass transition temperatures (T_g) were lowered to the range of 63–184 °C, close to those (65–178 °C) of commercial materials. Moreover, these terpolymers exhibited high refractive indices (1.627–1.675 at 589 nm) and excellent optical transparency (up to 96 % at 400 nm). A high tensile strength of 52.0 MPa was achieved, along with a strain at break value of ε = 5.0 %. This strategy effectively reduced the T_g of cyclic olefin copolymers, promoting the possibility of processing at lower temperatures. More importantly, optical and mechanical properties were maintained. The developed terpolymers are particularly promising for applications in optical devices, such as high-performance lenses and advanced display technologies.