US EPA

4937357 

Journal Article 

LIQUID-CRYSTALLINE SOLVENTS AS MECHANISTIC PROBES .40. DYNAMIC AND STATIC FLUORESCENCE FROM OMEGA-(1-PYRENYL)ALKANOIC ACIDS AND NONANCHORED PYRENYL MOLECULES AS PROBES OF LOCAL ENVIRONMENTS AND PHASE-CHANGES IN THE GEL AND MIDDLE PHASES OF AQUEOUS POTASSIUM STEARATE, RUBIDIUM STEARATE, AND POTASSIUM STEARATE 1-OCTADECANOL 

Jenkins, RM; Weiss, RG 

1990 

1 

Langmuir
ISSN: 0743-7463
EISSN: 1520-5827 

6 

8 

1408-1416 

English 

10.1021/la00098a015 

WOS:A1990DV28000015 

Static and dynamic fluorescence from three ω-(1-pyrenyl)alkanoic acids ((1-pyrenyl)acetic acid, 4-(l-pyrenyl)butanoic acid, and 12-(l-pyrenyl)dodecanoic acid), 1-dodecylpyrene, and pyrene, present in very low concentrations within nitrogen-saturated model bilayers, have been used to determine the local environment experienced by pyrenyl groups embedded at various positions in organized layers. The surfactant systems are the gel and middle phases of 50% by weight aqueous potassium stearate, rubidium stearate, and 1/1 potassium stearate/ 1-octadecanol. The results indicate that not all the “anchored” probes adopt extended conformations in the well-ordered gel phases and that chain melting attending the gel-middle phase transitions can be followed in detail from variations in probe fluorescence lifetimes. Surprisingly, structural changes that occur during the gel-middle phase transition can lead to very large increases in probe lifetimes even though one might anticipate a decrease in the total system order. An explanation of this and other unexpected results (based upon changes in the concentration of aqueous quenchers accessible to pyrenyl singlets) is advanced. © 1990, American Chemical Society. All rights reserved.