Transparent, intrinsically fire-safe yet impact-resistant poly(carbonates-b-siloxanes) containing Schiff-base and naphthalene-sulfonate

Abstract

A series of transparent, intrinsically flame-retardant, and impact-resistant poly(carbonates-b-siloxanes) were synthesized by incorporating Schiff-base modified polysiloxanes (DMS-Schiff) and naphthalene-sulfonate units into the polycarbonate (PC) chain. In addition to high transparency, the resultant copolymers (SS-co-PC5, SS-co-PC9, SS-co-PC14, and SS-co-PC20) exhibited remarkable improvements in fire safety and mechanical performance. Compared to pure PC, these copolymers demonstrated significantly enhanced limiting oxygen index (LOI, up to 34.5%) and a UL-94 V-0 rating under a thickness of only 1.6 mm. The incorporation of the polysiloxane blocks not only improved flame retardancy but also enhanced the impact strength, with SS-co-PC9 showing a 48% increase in elongation at break and a 38% rise in impact toughness compared to pure PC. In addition, SS-co-PC9 presented high mechanical strength. The synergistic effects between the naphthalene-sulfonate and polysiloxane blocks, along with the well-controlled polysiloxane phase separation (sulfonate units enabled lower processing viscosity of copolymers), led to superior comprehensive performance. These findings provide a promising pathway to create high-performance copolycarbonates for real-world applications.