Highly Refractive Polyimides Derived from Efficient Catalyst-Free Thiol–Yne Click Polymerization

Abstract

Polyimides (PIs), owing to their inherent high refractive index and excellent physical properties, are required in advanced optical applications. They are traditionally synthesized through conventional two-step polycondensation, followed by high-temperature or chemical imidization, inevitably increasing energy consumption, environmental pollution, and production duration. Herein, for the first time, we synthesized PIs consisting of vinylene sulfide linkages via an efficient catalyst-free thiol–yne click polymerization, which would be accomplished within 2 h at 25 °C by simply mixing the dithiols and bisimide-containing diynes in THF, affording PIs with tensile strength ranging from 106.3 to 114.9 MPa, glass transition temperature up to 238 °C, thermal decomposition temperature as high as 381 °C, and desirable solubility, so that it was easily cast from solution into tough films. Moreover, the BPADA-TBT PI film demonstrates good optical performance, with its refractive index exceeding 1.70 at 633 nm and transmittance above 81% at 450 nm, making it a potential candidate in advanced optical applications.