Supramolecular assemblies from amphiphiles

Lee, M. Lee, S.-J. Jiang, L.-H. Stimuh-responsive supramolecular nanocapsules from amphiphilic calixarene assembly. J. Am. Chem. Soc. 2004,126,12724-12725. 

When OG is added to the bicontinuous bilayer GMO supramolecular assembly, this amphiphile is expected to incorporate into the lipid membrane [19]. According to previous reports [8], the bilayer thickness of the mixed GMO/OG membrane is in the range 3.2-3.5 nm. Therefore, a half of this bilayer thickness will sterically fit to the radius of gyration of the OG micelle (1.6-1.7 nm). From a steric point of view, the ability of the glycerol monooleate bilayer to accommodate OG molecules is evidenced by the fact that it exceeds the length of the OG amphiphile (Scheme 1). 

Hierarchical Higher Organization - From Bilayers to Fibers and Rods Amphiphile assembly sometimes results in higher order supramolecular assemblies. Fibrous structures and helical ribbons with molecular dimensions are formed spontaneously. 

Phospholipids exhibit an excellent abihty to form liposome structures and are common in naturally-occurring cell membranes. The reason that nature uses phospholipids in the cell membrane is partly based on evolution-related biosynthetic requirements. From a physicochemical point of view, an amphiphile can form a liposome-hke supramolecular assembly as long as the amphiphile satisfies various structural requirements. Indeed, it has been found that a much simpler molecule - an ammonium salt with two long alkyl tails - can also form liposome-like assembhes. Therefore, structures simi-... 

Self-assembled structures are supramolecular assemblies of covalent backbones structured through intra- and interchain noncovalent interactions. These secondary structures arise from steric constraints and a network of weak interactions (i.e., hydrogen or Van der Waals bonding, dipole-dipole or amphiphilic interactions). Helical morphologies are stiU rarely represented in these artificial species but the control of the heHx sense, and a better knowledge of the chiral amplification mechanism, is highly desirable due to their potential use in many applications. For example, helically chiral polymers can be used as chiral stationary phases for HPLC or for catalysis. 

Self-assembly is used to organize molecules into amazing and complex structures. Small molecular weight molecules can be assembled into structures of varying degrees from dimers and trimers all the way up to and including supramolecular polymers. Simple amphiphiles form micelles and vesicles. Dendrimers, DNA-based materials, peptides, and peptides amphiphiles have been assembled into nanostructured fibrals reminiscent of the extracellular matrix. Obviously, we cannot cover here even a fraction of the creative and functional assembled systems reported. In this section, we highlight selected symmetrical self-assembled systems to illustrate how different... 

Polymersomes can also be assembled from large supramolecular amphiphiles. Recently, an elegant method for the preparation of vesicles through self-assembly of supramolecular graft copolymers was developed. ... 

The inherent ability of block copolymers to self-assemble into various well-ordered supramolecular structures makes them attractive for numerous technological applications. For instance, thin films self-assembled from block copolymers have been used as building blocks in nanotechnology and materials science [89-91 ]. Block copolymers have been employed directly without further manipulation as nanomaterials [92], or used as self-organized templates for the creation of nanos-tructured materials [92, 93]. Block copolymer blends demonstrated their applicability as patterning templates for the fabrication of well-ordered arrays [94], as well as for nanoscale manufacturing of more complex patterns [95]. The use of amphiphilic block copolymers for templating applications has been reviewed by FOrster [96]. 

If the copolymer is water soluble, the easiest method for generating polymersomes is direct dissolution of the dry polymer in aqueous media. However, this method cannot be used for insoluble water amphiphilic block-copolymers, for which a solvent-free or a solvent displacement method must be used. With the solvent-free method, a homogeneous amphiphilic polymer film is first deposited on a solid surface, and then subsequently hydrated in an aqueous buffer solution to form supramolecular assemblies upon desorption from the support. This is the method of choice when working under organic solvent-free conditions is mandatory, as for example for the combination with biomolecules. " When applying the solvent displacement method, the copolymer is first dissolved in an appropriate solvent, and then slowly mixed with water the reduced solubility of the copolymer drives the self-assembly process and formation of supramolecular assemblies, such as polymersomes. The organic solvent is eventually extracted, but complete removal of solvent traces is not possible and traces of organic solvents could affect sensitive biomolecules. 

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