title: A novel pyrene-based fluorescing amphiphile with unusual bulk and interfacial properties.
abstract: We have synthesised a new, pyrene-based, low-molecular-mass, amphiphilic molecule that displays a wealth of properties of potential interest for aggregation and interfacial applications. In order to elucidate some of the key properties of this molecule, which consists of a pyrene-containing hydrophobic head and a short PEG-based hydrophilic tail, we investigate herein some aspects of its concentration-dependent behaviour in aqueous solutions. We show that the inclusion of the hydrophobic pyrene group not only provides the molecule with intriguing bulk and interfacial properties down to low concentrations, but also with various means of assessing its aggregation behaviour by means of its well-characterised fluorescence properties. Combining a range of fluorescence techniques with microscopic imaging (optical and Cryo-TEM), interfacial tension measurements and foaming studies, we have been able to identify and characterise three concentration-dependant regimes. At low concentrations, the molecule is dissolved in monomeric form. At intermediate concentrations, labile aggregates are formed, which, at higher concentrations, give way to aggregates containing pre-associated pyrenes. Our measurements strongly imply that the latter aggregates are hexagonally close-packed tubular micelles. In this latter regime we also find a range of micron-sized precipitates. Additionally, the molecule displays strong interfacial activity, yet a surprisingly slow dynamics of interfacial adsorption. Finally, we demonstrate the possibility of using it to visualize interfaces and also create reasonably stable (1 hour) and fluorescing foams.
authors.affiliation: Laboratoire de Physique des Solides, UMR 8502, Université Paris-Sud, Bâtiment 510, 91405 Orsay cedex, France. salonen@lps.u-psud.fr
authors.forename: Anniina
authors.initials: A
authors.lastname: Salonen
authors.forename: Anton
authors.initials: A
authors.lastname: Knyazev
authors.forename: Nicolas
authors.initials: N
authors.lastname: von Bandel
authors.forename: Jéril
authors.initials: J
authors.lastname: Degrouard
authors.forename: Dominique
authors.initials: D
authors.lastname: Langevin
authors.forename: Wiebke
authors.initials: W
authors.lastname: Drenckhan
mesh_terms: D005453:Fluorescence; D005456:Fluorescent Dyes / Q000138:chemical synthesis / Q000737:chemistry*; D015394:Molecular Structure; D008970:Molecular Weight; D010316:Particle Size; D011092:Polyethylene Glycols / Q000737:chemistry; D011721:Pyrenes / Q000737:chemistry*; D013050:Spectrometry, Fluorescence; D013499:Surface Properties
chemical_list: D005456:Fluorescent Dyes; D011721:Pyrenes; D011092:Polyethylene Glycols; C030984:pyrene