Synthesis of a bi-functional terminal polyhedral octasilicate-core dendrimer containing carbazole and 1,8-naphthalimide, and its photoluminescence properties, film formability, and glass transition behavior

Abstract

The bi-functional terminal polyhedral octasilicate (OS)-core dendrimer containing carbazole and 1,8-naphthalimide on its peripheries, denoted by OS-NC, was synthesized by the combination of a ring-opening reaction and the condensation reaction of octakis(propenyl succinicanhydro)polyhedral octasilicate (OS-SA) with 9H-carbazole-9-ethanol and N-(hydroxyethyl)-1,8-naphthalimide. The binary blend of the same molar amounts of individual constituent OS-core dendrimers (carbazole-terminated OS-core dendrimer and 1,8-naphthalimide-terminated OS-core dendrimer) was also prepared. The coating film of OS-NC was easily peeled off from the substrate and formed a free-standing film, while the binary blend of the same molar amounts formed a waxy solid. Despite the utilization of intermolecular donor–acceptor interactions, the glass transition temperature (T_g) of the binary blends obeys the Kwei equation with a negative q value. The photoluminescence spectrum of OS-NC and the binary blends in the film state showed exciplex emission. In particular, OS-NC showed a larger red-shift emission than the binary blends.