PHOTOPHYSICS OF PREASSOCIATED PYRENES IN AQUEOUS POLYMER-SOLUTIONS AND IN OTHER ORGANIZED MEDIA

The objective of this review has been to characterize the photophysics of the excimer originating from pyrene in organized systems. From this survey emerges a unified description of the spectroscopy of associated pyrenes, whether the association occurs in a pyrene crystal, in a single molecule, such as a pyrenophane or a bis-alkylpyrenyl derivative, in pyrene-doped monolayers, or in aqueous solutions of pyrene-labeled polymers. Key photophysical parameters useful in detecting pyrene preassociation were defined. Their application was illustrated with examples taken from the field of pyrene-labeled water-soluble polymers. The emphasis of the review was placed on pyrene, but in an organized environment other chromophores, anthracene or naphthalene for example, exhibit similar spectroscopic features. Although this is a clear restriction, it is justified by the current widespread use of pyrene fluorescence as a tool in polymer science. Ground-state association of pyrene in dilute solutions of labeled polymers was perceived as an unusual occurrence less than 10 years ago. The number and variety of examples cited in this review are witnesses to the fact that the phenomenon is in fact quite common. Given the practical importance of hydrophobically-modified polymers, one can anticipate further activity in the use of pyrene as an aid to understand the properties of these polymeric systems. © 1993, American Chemical Society. All rights reserved.