Self-Assembly of Macromolecular Structures

A classic example of the formation of a macrocycle by a neutral template is that of the versatile host compound and component of molecular machines, the so-called blue box, or cyclobis paraquat-para-phenylene. Reaction of the horseshoe precursor with dibromo-para-xylene leads to the formation of a tricationic intermediate that is capable of binding the template molecule (Scheme 3), which closes the macrocycle to form the tetracationic cyclophane. The jT-ir interactions of the charge-transfer variety (the complex of the product and template is colored, whereas the components are not) assisted by the charge on ihe product are a major driving force in the process, as revealed in X-ray structures of complexes. It should be noted that the interaction is of the jr-n type assisted by the complementary positive charge on the bipyridinium residues and r-electron-rich nature of the template. This supramolecu-lar synthon can be used for other cyclophanes, catenanes, and rotaxanes (see Self-Assembly of Macromolecular Threaded Systems, Self-Assembled Links Catenanes, and Rotaxanes—Self-Assembled Links, Self-Processes). 

Figure 5 Toward applications of self-assembled DNA systems, (a) Attachment of different sized gold nanoparticles to DNA and self-assembly of antennae structures, (b) DNA origami can be modified with multiple aptamers to produce stronger bivalent protein interactions, (c) Viruses can be specifically arranged on DNA origami, (d) Nanoparticles functionalized with DNA can be assembled into highly crystalline networks, (e) Using DNA, a well-ordered macromolecular 3D crystalline lattice can be assembled.

Since the literature on the common block copolymer micellar structures is vast, only a limited number of examples will be given, in order to outline the fundamental principles behind the self-assembly of macromolecular chains. Moreover, the so-called common polymeric nanostructures have been described in detail by a number of review articles and books, which are strongly recommended for further reading [1 ]. The story of self-assembly is tightly connected with the story of... 

Recently, we have also prepared nanosized polymersomes through self-assembly of star-shaped PEG-b-PLLA block copolymers (eight-arm PEG-b-PLLA) using a film hydration technique [233]. The polymersomes can encapsulate FITC-labeled Dex, as model of a water-soluble macromolecular (bug, into the hydrophilic interior space. The eight-arm PEG-b-PLLA polymersomes showed relatively high stability compared to that of polymersomes of linear PEG-b-PLLA copolymers with the equal volume fraction. Furthermore, we have developed a novel type of polymersome of amphiphilic polyrotaxane (PRX) composed of PLLA-b-PEG-b-PLLA triblock copolymer and a-cyclodextrin (a-CD) [234]. These polymersomes possess unique structures the surface is covered by PRX structures with multiple a-CDs threaded onto the PEG chain. Since the a-CDs are not covalently bound to the PEG chain, they can slide and rotate along the PEG chain, which forms the outer shell of the polymersomes [235,236]. Thus, the polymersomes could be a novel functional biomedical nanomaterial having a dynamic surface. 

When the composite-matrix is formed with a polystyrene solution as a dispersion medium, the self-assembly of silica particles is influenced by the adsorption of macromolecules on their surface. During adsorption, both solitary macromolecules and their aggregates transfer simultaneously onto the adsorbent surface. Depending on solution concentration, not only the conformation of adsorbed molecules but also the number and size of macromolecular aggregates in the solution change on adsorption. This leads to the formation of complex-shaped structures, which are linked by a system of nonvalent interactions and consist of polymeric-inorganic blocks[8,14] this is of interest in the preparation of a nanostructured medium (polystyrene-silica gel) as a precomposite for the fabrication of carbon structures in a matrix of silica particles. 

Self-assembled macromolecular structures are of particular interest because of their ability to reorganize in response to changes in their environment (concentration, solvent, pH, etc.)415-416 Zimmerman and co-workers417 418 first demonstrated the hydrogen-bond mediated self-assembly of dendritic cores (Figure 22) in 1996. The rigid bis(isophthalic acid)... 

A broad view of principal findings and processes utilized for the development of oriented polymer morphologies has been presented. New trends toward the advancement of this topic are being developed within the realm of multidisciplinary research. Studies of order development in polymers have—for a few years already—transcended beyond traditional disciplines in chemistry and engineering. Genetically engineered polymers, nanoparticles, self-assembled molecules, supercritical fluids, and hybrids are some of the few areas that are now an integral part of macromolecular structural property relationship studies. 

Several sessions were included in scientific program. The session Bio-inspired Polymers included 11 oral presentations. Self-assembly of an aquaporin mimic, tailoring surface properties with polymer brushes, bioinspired block copolymers, hierarchically structured conjugated polymers via supramolecular self-assembly, natural polymeric composites with mechanical function, macromolecular oxidation catalysts based on miniemulsion polymerization and some other problems were discussed on this session. 

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