Generate Rich Fluorescence in a Simple Polystyrene System through Solvent Removal and Molecular Interactions

Abstract

With solvent evaporation, polystyrene fine particles are found to exhibit an unusual fluorescence change from possessing a typical excimer emission band centered at 330 nm to a variety of strong structured bands at longer wavelength with maxima at 356 nm, 365 nm, 372 nm, 383 nm, 404 nm and 426 nm. Similar fluorescence emissions are also observed in polystyrene film after solvent removal. The excita-tion spectra observed by monitoring these fluore-scence emissions at the wavelengths of maxima reveal fluorescence is emitted from different fluoro-phores. The folding of polystyrene chains during the preparation of polystyrene fine particles through reprecipitation and polystyrene chain relaxation during solvent evaporation are believed to be prerequisites for the formation of different fluoro-phores via phenyl aggregations, while the aromatic-aromatic interactions between the pendant phenyl groups on polystyrene chains are considered to bring a powerful driving force for the formation of fluorophorous phenyl aggregations responsible for the observed fluorescence phenomena. This dis-covery can contribute to understanding and control of molecular interactions in aromatic systems, especially aromatic macromolecule systems. The luminescence can be used to manufacture light devices and other hybrid materials, as well as to probe local environment in aromatic systems.