Difluoroboron Dibenzoylmethane PCL-PLA Block Copolymers: Matrix Effects on Room Temperature Phosphorescence

Abstract

Luminescent materials result when boron dyes are combined with polyester biomaterials. Previously, it was reported that difluoroboron dibenzoylmethane polylactide, BF2dbmPLA, exhibits intense fluorescence as well as unusual room temperature phosphorescence (RTP) in the solid state. To gain a better understanding of polymer effects on photophysical properties, a poly(ε-caprolactone) (PCL) analogue, BF2dbmPCL, was synthesized by tin catalyzed ring-opening polymerization and employed as a macroinitiator in combination with d,l- and l-lactide for the preparation of BF2dbmPCL-PLA and BF2dbmPCL-PLLA block copolymers, respectively. Reasonably well-defined materials with low polydispersity indices (PDIs) were obtained in good yield. 1H NMR and UV−vis spectroscopy and thermal analysis are reported. Luminescence spectra and lifetimes were measured for polymer solutions and films. All materials are intensely fluorescent with high quantum yields. Although no RTP is noted for BF2dbmPCL films, curiously, this property is restored for PCL-polylactide block copolymer analogues in the solid state.