Molecular orientation in heavy ion tracks

By using polarized fluorescence methods the orientation properties of molec ular probes incorporated in heavy ion tracks were investigated. For the inv estigations poly(ethylene-terephthalate) (PET) was chosen as a polymer with well characterized fluorescence properties. Fluorescence probes such as am inostyryl-derivatives were incorporated in heavy ion tracks by using a suit able solvent, e.g. N, N'-dimethylformamide (DMF) as transport medium. By me ans of polarized fluorescence spectroscopy it is shown that deposited molec ular probes with a high aspect ratio have a preferential orientation parall el to the ion track axis. The orientation of the molecular probes indicates that molecules can be aligned in ion tracks without interdiffusion into th e surrounding material. It can be shown that this orientation is sensitive to an overlapping of the tracks. By this a track radius of about 18 nm can be determined, The orientation of the fluorophores correlates with the amou nt of overlapping tracks. (C) 1998 Elsevier Science B.V. All rights reserve d.