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

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.