Supramolecular assemblies from morphology

Morphologically diverse supramolecular assemblies have been formed from long-chain chiral aldonamides [370-378]. Typical compounds include 28 30. Formation of 200- and 300-A-diameter rods and helical rope-like structures in aqueous n-octyl- and n-dodecyl-D-gluconamide (D-28-8 and D-28-12) gpls has been recognized for some time [379]. In a subsequent work, helical double-... 

The authors also reported on the supramolecular self-assembly from rod—coil—rod triblock copolymers prepared by copolymerization of 5-acetyl-2-aminob-ezophenone with diacetyl functionalized polystyrene with low polydispersity (Scheme 12).110 In contrast to the rod—coil diblock copolymers which exhibit multiple morphologies, the triblock copolymers were found to spontaneously form only microcapsules or spherical vesicles in solution as evidenced by optical polarized, fluorescence optical, and scanning electron microscopies (Figure 33). 

The physical manipulation of predefined nanoscopic objects allows for an enhancement in the diversity of stmctures, beyond those that are readily accessible by direct covalent chemistry or supramolecular assembly. The entire Section 6.20.2 describes variations in the architectures of the polymer building blocks and conditions during their supramolecular assembly to afford nanoscopic objects, having different sizes, shapes, morphologies, and so on. An alternative approach is to produce an initial nanostructure and then alter its properties. This approach brings concepts from the templating techniques for the shaping of preestablished nano- or microscopic particles, as discussed in Section 6.20.2.3 vide supra). 

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. 

A brief inspection of Fig. 5 reveals that these supramolecular structures could be similar to those self-assembled from block copolymers. Two major differences exist between self-assembling dendrons and block copolymers. First, all structures in Fig. 4 are generated from the same chemical composition but different primary structure, including constitutional isomeric primary structures, and secmid, they exhibit intramolecular order. Block copolymers provide micellar morphologies with different stractures determined by different ratios between their dissimilar segments. 

Figure 6.4 Schematic representation of (a) core-shell morphology and (b) temperature-responsive supramolecular self-assembly of arborescent PS-gro/i-P2VP5 copolymers in toluene. (Reprinted with permission from S.I. Yun, G.E. Gadd, V. Lo et al, Temperature-responsive supramolecular assembly of dendrigraft micelles with a solvophilic core -solvophobic shell structure, Macromolecules, 41, 7166-7172. 2008 American Chemical Society.) (Colour version of this figure is available on the book companion web site.)...

In this volume we have collected 10 review chapters from distinguished scientists who have contributed extensively to the study and development of supramolecular assemblies that contain metals and metal-like elements with unusual structures and morphologies and possess potentially useful (and applicable) physical and biological properties. The first chapter by K. Ariga et al. is a general discussion of supramolecular structures that contain inorganic building blocks for hybrid lipid thin films, layer-by-layer assemblies, structure transcription, and functional mesoporous hybrids. This is followed by two chapters, the first by M. L. Kistler et al., who describe the self-assembly of hydrophilic polyoxometalate (POM) macro-anions and examine the structure and behavior of POM macro-ions in solution. This is followed by a chapter by S. K. Das, who provides an overview of the supramolecular features of POM-supported transition metal complexes, POM-crown ether complexes with supramolecular cations, and supramolecular water clusters associated with POMs. 

Fig. 15.5. Schematic models of supramolecular fibrillar assemblies of Afi(l-40) fibrils. Variation in morphology can arise at the level of oligomeric species, protofilaments, or initial short fibrils. They associate together on the quartz surface, creating three types of supramolecular fibrillar assemblies Straight fibrils (Type I), spherulitic assemblies (Type II), and worm-like fibrils (Type III). A mixed architecture of type I and fibrils (Type I/II) was also observed when the internal density is coarse. It is to be noted that the different precursors are represented together in a box and that the relationships between amyloid precursors and final products remain unclear. Reproduced from [18] with permission...

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