Organized Collapse Structures in Mixtures of Chiral Ethyl 2-Azido-4-fluoro-3-hydroxystearates

Abstract

Monolayers of enantiomeric compounds as well as diastereomeric mixtures and racemic/diastereomeric mixtures of ethyl 2-azido-4-fluoro-3-hydroxystearates have been investigated using surface pressure-area isotherms and Brewster angle microscopy. All monolayers collapse out of the liquid-expanded phase, forming 3D collapse structures which were visualized with scanning force microscopy. The enantiomeric compound and the diastereomeric mixtures form unique fiber-like network structures with heights between 20 and 40 nm. Interestingly, the shape of the enantiomeric fiber structures is straight, whereas the diastereomeric mixtures exhibit curved fibers of different sizes. The racemic mixture however forms circular 10 nm high and 20-50 microm broad structures. The shape of unconventional collapse structures could be changed by using distinct ratios of diastereomeric or racemic/diastereomeric mixed compounds.

Langmuir monolayer miscibility of single-chain partially fluorinated amphiphiles with tetradecanoic acid

“…In the present study, the both mixtures of MA/F8C5OH and MA/F8C5PC generate fern-like networks as 3-D structures. The fern-like networks resemble fiber-like networks, which is formed on single monolayers of 2-azido-4-fluoro-3-hydroxystearates (EAFHSs) [70] in their growth and shape, although the present systems contain two components. Considering no appearance of 3-D collapsed structures for pure components investigated, the formation of the structures as observed in Fig.…”

“…In particular, pure components except for isomeric molecular species containing enantiomer and diastereoisomer have been extensively examined to obtain a thorough understanding of the collapse mechanism. Over-compression above the monolayer collapse pressure produces a remarkably rich variety of 3-D structures such as vesicle [69], giant folds [64], fiber-like networks [70], and so on. In the present study, the both mixtures of MA/F8C5OH and MA/F8C5PC generate fern-like networks as 3-D structures.…”

Organization of the enantiomeric and racemic forms of an amphiphilic resorcinol derivative at the air–water and graphite–1‐phenyloctane interfaces

“…Further compression results in a homogeneous thin film (crystal-like solid phase) without any black spots (which represents the water subphase). Then at higher surface pressure the monolayer undergoes a transformation, and, because of the collapse of the film, 25 a few white spots appear. The images suggest well shaped condensed phase domains, which mean a highly ordered molecular packing is found for the enantiomers and the racemic mixture.…”

Chiral recognition at the air–water interface

“…1B(b)). Similarly, Haufe demonstrated the formation of controlled three-dimensional structures as the result of interaction of chiral components within a twodimensional monolayer plane [21]. They investigated the morphologies of collapsed phases of monolayers of enantiomeric compounds as well as diastereomeric mixtures and racemic/diastereomeric mixtures of ethyl 2-azido-4-fluoro-3-hydroxystearates.…”