Preparation and Properties of High Refractive Index and Temperature‐Resistant Polycarbonate Containing Fluorene

To develop a polycarbonate with a high refractive index and good heat resistance, 9,9‐di[3‐phenyl‐4‐(2‐hydroxyethoxy)phenyl]fluorene (BPPEF) and diphenyl carbonate were used as monomers, and BPPEF‐based polycarbonate (BPPEF‐PC) was prepared by melt transesterification polycondensation. The effects of polymerization processes on the molecular weight of polymers were investigated. The structure of BPPEF‐PC was characterized, and the thermal properties, solubility, optical properties, dielectric properties, and mechanical properties of BPPEF‐PCs with different molecular weights were measured. The chemical structure of BPPEF‐PC is as expected and belongs to an amorphous polymer. The introduction of the cardo structure into the polymer backbone greatly increased the refractive index of polycarbonate, and the thermal resistance was also improved. The refractive index of BPPEF‐PC is up to 1.656, and the transmittance ( T 500 ) is up to 88% (38 μm), showing lower haze and yellow index. Its glass transition temperature is up to 160°C, and the 5% mass loss temperature is up to 407°C in an N 2 atmosphere. In addition, its dielectric constant and dielectric loss (15 GHz) are about 3.06 and 0.012, respectively. As the molecular weight increases from 2.2 × 10 4 to 5.3 × 10 4 g mol −1 , the elongation at break of BPPEF‐PCs increases from 1.2% to 3.3%, and the tensile strength increases from 23 to 72 MPa.