AN EASY METHOD TO MONITOR LACTIDE POLYMERIZATION WITH A BORON FLUORESCENT PROBE

摘要

Fluorescence spectroscopy has been widely used to monitor different polymer processes such as polymerization kinetics, chain entanglements, and thermal transitions. The solvent free ring-opening polymerization (ROP) of lactide is significant both commercially and for research; thus, monitoring this process with a simple fluorescence method can be very useful. Here a fluorescent dye, difluoroboron 4-methoxydibenzoylmethane (BF_2dbmOMe) is employed to probe lactide bulk ROP by measuring emission from a solidified reaction aliquot at room temperature. It was found that through the course of the polymerization, the solid-state fluorescence of BF_2dbmOMe in the aliquots exhibited a systematic shift from yellow to green to blue, accompanied by a gradual reduction in decay lifetime. The fluorescence color change is sensitive to the monomer percentage conversion, not polymer molecular weight. Based on these observations and experimental data, we propose that the long wavelength emission with perceivably longer lifetimes arises from BF_2dbmOMe dye aggregates (ground and/or excited states), while the dissolved individual dye molecules are responsible for the blue fluorescence with a shorter lifetime. This demonstration of the utility of BF_2dbmOMe as a fluorescent probe for lactide polymerization could have important practical implications. polylactide, ring-opening polymerization,fluorescence spectroscopy