Fluorocarbon amphiphiles

Laschewsky A, Ringsdorf H and Schmidt G 1985 Polymerization of hydroxocarbon and fluorocarbon amphiphiles in Langmuir-Blodgett multilayers Thin Soiid Fiims 134 153-72... 

FIG. 8 Force-distance dependence for surfaces covered with fluorocarbon amphiphile 1 in pure water (1) and in aqueous solutions containing 0.7 mg/L poly (styrenesulfonate) (2) and 7.0 g/L poly (styrenesulfonate) (3). The molecular weight of the polymer is 5 X ICP. Lines are drawn as a visual guide. 

LB Mono- and Multilayers of Fluorocarbon Amphiphilic Polymers and Their Application in Photogalvanic Metal-Insulator-Seminconductor Structures... 

Fig. 70. Schematic representation of the structure of the outermost layer of the composite thin film with small and large weight percents of fluorocarbon amphiphile [437]...

Phase-separated monolayers and liposomes were characterized by R. Elbert1011 who synthesized saturated and polymerizable fluorocarbon amphiphiles (59, 60, 61) and investigated their mixing behavior with CH2-analogues and natural lipids. In these systems the fluorocarbon compounds are incompatible with hydrocarbon lipids in a wide range of compositions and tend to form domains of pure fluorocarbon and hydrocarbon amphiphiles. The domains can be visualized by freeze-fracture electron microscopy. 

Y. Ishikawa, H. Kuwahara, T. Kunitake, Self-Assembly of BUayers from Double-Chain Fluorocarbon Amphiphiles in Aprotic Organic Solvents Thermodynamic Origin and Generalization of the Bilayer Assembly , J. Am. Chem. Soc., 116,5579 (1994)... 

Most LB-forming amphiphiles have hydrophobic tails, leaving a very hydrophobic surface. In order to introduce polarity to the final surface, one needs to incorporate bipolar components that would not normally form LB films on their own. Berg and co-workers have partly surmounted this problem with two- and three-component mixtures of fatty acids, amines, and bipolar alcohols [175, 176]. Interestingly, the type of deposition depends on the contact angle of the substrate, and, thus, when relatively polar monolayers are formed, they are deposited as Z-type multilayers. Phase-separated LB films of hydrocarbon-fluorocarbon mixtures provide selective adsorption sites for macromolecules, due to the formation of a step site at the domain boundary [177]. 

The process of adsorption of polyelectrolytes on solid surfaces has been intensively studied because of its importance in technology, including steric stabilization of colloid particles [3,4]. This process has attracted increasing attention because of the recently developed, sophisticated use of polyelectrolyte adsorption alternate layer-by-layer adsorption [7] and stabilization of surfactant monolayers at the air-water interface [26], Surface forces measurement has been performed to study the adsorption process of a negatively charged polymer, poly(styrene sulfonate) (PSS), on a cationic monolayer of fluorocarbon ammonium amphiphilic 1 (Fig. 7) [27],... 

FIG. 7 Chemical structures of fluorocarbon ammonium amphiphile 1 and poly(styrene sulfonate) (PSS). 

Finally, we have designed and synthesized a series of block copolymer surfactants for C02 applications. It was anticipated that these materials would self-assemble in a C02 continuous phase to form micelles with a C02-phobic core and a C02-philic corona. For example, fluorocarbon-hydrocarbon block copolymers of PFOA and PS were synthesized utilizing controlled free radical methods [104]. Small angle neutron scattering studies have demonstrated that block copolymers of this type do indeed self-assemble in solution to form multimolecular micelles [117]. Figure 5 depicts a schematic representation of the micelles formed by these amphiphilic diblock copolymers in C02. Another block copolymer which has proven useful in the stabilization of colloidal particles is the siloxane based stabilizer PS-fr-PDMS [118,119]. Chemical... 

In the present review, first we will describe how to fabricate artificial photosynthetic reaction center in nanometer scales by making use of phase separation in mixed monolayers of hydrocarbon (HC) and fluorocarbon (FC) amphiphiles [2,5,20-26] as shown in Fig. 2b [3]. The phase separated structures were studied by SPMs such as AFM, SSPM, and scanning near-field optical/atomic force microscopy (SNOAM) [27-33] as well as a conventional local surface analysis by SIMS [3,5], The model anionic and cationic HC amphiphilic... 

The reason for Nafion LB-film fabrication was the wish to obtain the highly ordered systems from perfluorinated ion exchange polymer with multilayered structure, where the ionic layers (conductors) would alternate with fluorocarbon polymer layers (insulators), and to investigate the properties of such films.74 This polymer contains a hydrophobic fluorocarbon polymeric chain and hydrophilic ionic groups, so it is sufficiently amphiphilic it has a comblike structure that makes it a suitable polymer for LB-film deposition. 

M.P. Krafft, Fluorocarbons and fluorinated amphiphiles in drug delivery and biomedical research, Adv. Drug Deliv. Rev. 47 (2001) 209-228. 

The extensive studies of the behavior of mixed monolayers or bilayers of di-acetylenic lipids and other amphiphiles parallel to some degree the studies of dienoyl-substituted amphiphiles. Since the dienoyl lipids do not contain a rigid diacetylenic group in the middle of the hydrophobic chains, they tend to be miscible with other lipids over a wide range of temperatures and compositions. In order to decrease the lipid miscibility of certain dienoyl amphiphiles, Ringsdorf and coworkers utilized the well-known insolubility of hydrocarbons and fluorocarbons. Thus two amphiphiles were prepared, one with hydrocarbon chains and the other with fluorocarbon chains, in order to reduce their ability to mix with one another in the bilayer. Of course it is necessary to demonstrate that the lipids form a mixed lipid bilayer rather than independent structures. Elbert et al. used freeze fracture electron microscopy to demonstrate that a molar mixture of 95% DM PC and 5% of a fluorinated amphiphile formed phase-separated mixed bilayers [39]. Electron micrographs showed extensive regions of the ripple phase (Pb phase) of the DM PC and occasional smooth patches that were attributed to the fluorinated lipid. In some instances it is possible to... 

Fig. 8. Two pairs of a polymerizable zwitterionic dienoyl lipid and a cleavable disulfide amphiphile derived from cysteine. In each pair, one amphiphile has a hydrocarbon tail and the other a fluorocarbon tail.

Amphiphilic molecules, composed of a hydrophilic head group and hydrophobic chain (hydrocarton or fluorocarbon), have a tendency to aggregate at the air/water interface and, when compressed, form monomolecular Langmuir films. These films can be... 

Fluorocarbons and fluorinated amphiphiles have found a variety of applications in materials science and medicine [1-5]. As many of these applications involve colloidal systems stabilized by a monolayer of fluorinated amphiphiles, it is essential to understand the structure and properties of these interfacial films. Such knowledge can provide improved control over the engineering and properties of highly fluorinated colloids and interfaces [6]. 

A surfactant molecule is an amphiphile, which means it has a hydrophilic (water-soluble) moiety and a hydrophobic (water-insoluble) moiety separable by a mathematical surface. The hydrophobic tails of the most common surfactants are hydrocarbons. Fluorocarbon and perfluorocarbon tails are, however, not unusual. Because of the hydrophobic tail, a surfactant resists forming a molecular solution in water. The molecules will tend to migrate to any water-vapor interface available or, at sufficiently high concentration, the surfactant molecules will spontaneously aggregate into association colloids, i.e., into micelles or liquid crystals. Because of the hydrophilic head, a surfactant (with a hydrocarbon tail) will behave similarly when placed in oil or when put in solution with oil and water mixtures. Some common surfactants are sodium or potassium salts of long-chained fatty acids (soaps), sodium ethyl sulfates and sulfonates (detergents), alkyl polyethoxy alcohols, alkyl ammonium halides, and lecithins or phospholipids. 

The driving force for the formation of the hpid bilayer structure is the amphiphiUcity of the component molecules one part of the molecule is soluble in a particular solvent while the other has a low affinity to the solvent. If this concept is extended, the use of water as a medium is not a necessary condition of bilayer structure formation. Reversed micelles are formed in organic solvents. Are bilayer structures also formed in organic solvent This is an important question regarding the fundamental nature of amphiphilicity and the abihty to extend the applicability of amphiphile assembhes to various fields. The answer to this question is yes . Some compounds with a fluorocarbon part and a hydrocarbon part can form bilayer-like assemblies in organic solvent. The fluorocarbon part has a low affinity to the organic solvent and has a solvophobic nature, hi contrast, solvophilic characteristics are exhibited by the hydrocarbon parts. As shown in Fig. 4.30, these amphiphilic molecules assemble in order to expose the solvophilic part to the solvent and to hide the solvophobic part inside the assembly. If there is a good structural balance between the solvophilic part... 

Fluorinated surfactants (or fluorosurfactants, i.e., surfactants with hydrophobic tails comprising a fluorocarbon moiety) provide an alternative means of achieving extremely stable PFC emulsions, as they can provide very low PFC/water interfacial tensions [cr , another factor in Eq. (2)]. d s yet, this option has not been developed, in part because of the added cost involved in the evaluation for approval of a novel active excipient. A further means of effectively increasing the stability of EYP-based PFC emulsion consists of supplementing standard phospholipids with mixed fluorocarbon-hydrocarbon diblock compounds, such as 14 or 15. Such diblocks, which have fluorophilic-lipophilic amphiphilic properties, are expected to improve the adhesion of the phospholipid film onto the PFC droplet. 

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