Poly(dibenzothiophenylene sulfide)s: sulfur-rich annulated frameworks with a wide-range ultrahigh refractive index

Abstract

Poly(phenylene sulfide) (PPS) derivatives exhibit remarkable high-refractive properties due to their elevated sulfur content. However, their refractive indices (RIs) have typically been limited to n_D ∼ 1.7–1.8, primarily due to the sterically hindered side chains required for desirable amorphous properties. In this study, we demonstrate the “PPS-annulation” strategy, which involves the partial fused system of PPS, as a rational molecular design to achieve wide-wavelength ultrahigh RI. In short, poly(dibenzothiophene sulfide) (PDBTS), an annulated analog of PPS, is precisely synthesized through oxidative polymerization. PDBTS demonstrates an ultrahigh RI of n_D = 1.85, excellent thermostability (T_g = 205 °C), and a completely amorphous nature owing to its aromatic/sulfur-rich and rigid backbone. Furthermore, PDBTS is further functionalized through copolymerization with other PPS derivatives (e.g., hydroxy- or methylthio-substituted PPS) to optimize the balance between their ultrahigh RI (n_D over 1.82) and enhanced visible–near-infrared transparency. Overall, the “PPS-annulation” strategy offers a rational design for polymeric materials with enhanced RI, high thermostability, amorphous characteristics, and exceptional optical properties.