The Effect of Polycrystalline Nanoscale Zinc Sulfide on the Molecular Weight and Properties of Polycarbonate

Bis(4-(2-hydroxyethoxy)phenyl)fluorene polycarbonate is a transparent thermoplastic resin characterized by a high refractive index and low birefringence, yet it has a relatively low molecular weight. To further increase the polymer's molecular weight, this study synthesized α-ZnS and β-ZnS, along with their coexisting phase, through a precipitation method to catalyze the transesterification polycondensation of bisphenol A (BPA), 9,9-bis[4-(2-hydroxyethoxy)phenyl]fluorene (BPEF), and diphenyl carbonate (DPC) via melt ester exchange polycondensation. It was found that the acidic sites generated during calcination contribute to enhanced catalytic activity, leading to a high-molecular-weight polycarbonate ( M w = 87,363). Concurrently, the tensile strength (89.02 MPa) increased as the molecular weight rose. Notably, varying the ZnS content (0.085–1.67 g/kg) in the incorporated polycrystalline phase not only effectively catalyzed the polymerization reaction but also increased the refractive index without significantly affecting the transmittance. Highlights Polycrystalline ZnS was synthesized through precipitation and calcination for catalytic applications. The medium-strength acid sites on ZnS notably augmented the molecular weight of polycarbonate (PC). The high M w PC matrix elevated the tensile strength to 89.02 MPa. PC doping with ZnS increased the refractive index without a significant reduction in transmittance. The PC/ZnS composites demonstrated outstanding UV-shielding properties and thermal stability.