A Neutron Reflectivity Study of Spread Monolayers of Eicosanoic Acid, Valinomycin, and Their Equimolar Mixture
✍ Scribed by Archibald Eaglesham; Thelma M. Herrington
- Publisher
- Elsevier Science
- Year
- 1995
- Tongue
- English
- Weight
- 340 KB
- Volume
- 171
- Category
- Article
- ISSN
- 0021-9797
No coin nor oath required. For personal study only.
✦ Synopsis
Neutron reflectivity profiles and surface pressure ( (\Pi) )-area (A) isotherms were obtained for spread monolayers of eicosanoic acid, valinomycin, and their equimolar mixture at (\mathrm{pH} 5.8) and (296 \mathrm{~K}). The neutron data for the individual components showed that the molecules of deuterated eicosanoic acid were oriented almost vertically at a surface pressure as low as (12 \mathrm{mN} \mathrm{m}^{-1}), in agreement with the low compressibility of this portion of the II- (\boldsymbol{A}) isotherm, whereas the molecules of valinomycin lie flat in the surface. The (\Pi-\boldsymbol{A}) isotherm for the mixture was the average of that for the individual components, which implies little interaction between unlike molecules. It was not possible to model the neutron reflectivity data for this system using an intimately mixed monolayer of the two molecular species. However, the assumption that the monolayer consisted of separate islands of eicosanoic acid and valinomycin gave good-quality fits to the data on both a (\mathrm{D}_{2} \mathrm{O}) and a contrast-matched water subphase. This lack of cross interaction among the molecules of an archipelago of two species explains the П- (\boldsymbol{A}) data. (1995 Academic Pres, Inc.
Key Words: neutron reflectivity; equimolar mixture; eicosanoic acid; islands; valinomycin; archipelago.