Anionic surfactants, which are widely used as detergents and soap for cleaning processes, consist generally of negatively charged headgroups and positively charged counterions (such as sodium, potassium, or ammonium ions). For example, polyoxyethylene alkyl ethers,, are nonionic surfactants made of hydrophilic oxyethylene units and an alkyl chain with methylene groups (Figure 1(a)). A large variety of conventional nonionic surfactants consist generally of a hydrophilic poly(ethylene oxide) chain, often called ethoxylates, connected with a hydrophobic alkyl chain, and are generally used in cleaning applications with anionic surfactants. Nonionic surfactants have either polyether or polyhydroxyl units as the hydrophilic group. In conventional head/tail(s) amphiphiles the lipophilic part consists generally of a long (saturated or unsaturated) hydrocarbon chain, while the hydrophilic head can be either nonionic or ionic. Characteristic and Basic Properties of AmphiphilesĪmphiphiles are compounds possessing both hydrophilic (water-loving) and lipophilic (fat-loving) or water-hating components.
The reversibility of noncovalent interactions allows dynamic switching of nanostructures morphology and functions in response to various external stimuli which further provides a flexible platform for the design and fabrication of smart amphiphilic nanomaterials and functional supramolecular devices.
Finally, we provide insight into the novel structural features obtained by the precise tailoring of chemical structures and the efficient use of noncovalent forces for the introduction of chirality, signal processing, and recognition processes. Moreover, we highlight important examples where complex processes such as the structure modulation and control of morphology by other structure directing interactions can stimulate advanced application in materials science as well as in biological and medicinal chemistry. In the first part of this review we present a tutorial introduction to the basic aspect of traditional, head/tail(s) type, amphiphiles whose aggregation is driven by soft interactions such as hydrogen bonds and steric effects and hydrophobic and electrostatic interaction. Leading examples can be found in biosystems where assemblies of different amphiphilic macromolecular components and their integrated actions allow the performance of highly specific cellular functions. The thermodynamic incompatibility between the different blocks causes a spatial organization into ordered morphologies on the nanoscale with the production of novel structural features, as demonstrated by recent studies. Self-assembly processes involving amphiphilic macromolecules provide unique and new opportunities for designing novel materials for advanced application in nanotechnology. In this perspective, we summarize in this tutorial review the basic concept and recent research on self-assembly of traditional amphiphilic molecules (such as surfactants, amphiphile-like polymers, or lipids) and more recent concepts of supramolecular amphiphiles assembly which have become increasingly important in emerging nanotechnology. Leading examples of these novel self-assembly processes can be found, in fact, in biosystems where assemblies of different amphiphilic macrocomponents and their integrated actions allow the performance of highly specific biological functions.
Introduction of stimulus responsive supramolecular amphiphile assembly-disassembly processes provides particularly novel approaches for impacting bionanotechnology applications. While amphiphiles self-assembly has attracted considerable attention for decades due to their extensive applications in material science, drug and gene delivery, recent developments in nanoscience stimulated the combination of the simple approaches of amphiphile assembly with the advanced concept of supramolecular self-assembly for the development of more complex, hierarchical nanostructures. Self-assembly processes of amphiphiles have been widely used to mimic biological systems, such as assembly of lipids and proteins, while their integrated actions allow the performance of highly specific cellular functions which has paved a way for bottom-up bionanotechnology. Amphiphiles are synthetic or natural molecules with the ability to self-assemble into a wide variety of structures including micelles, vesicles, nanotubes, nanofibers, and lamellae.
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