Core-shell architectures

Figure 1.14 Three-dimensional projection of dendrimer core-shell architecture for G = 4.5 poly(amidomine) (PAMAM) dendrimer with principal architectural components (I) core, (II) interior and (III) surface...

Construction of organic nanotubes starting from porphyrin dendrimers with core/shell architecture is also feasible. Figure 8.29 also shows how covalent nanotubes can be produced by removal of the dendritic component of the molecule. A coordination polymer is first synthesised from a dendritic metallopor-phyrin with alkene end groups. This is subjected to intramolecular and intermo-lecular crosslinking by ring-closing metathesis at the periphery. 

Figure 11.17 (a) Schematic diagram showing the core-shell architecture of the pH sensing... 

Hydrophilic-hydrophobic diblock copolymers exhibit amphiphilic behavior and form micelles with a core-shell architecture. These polymeric carriers have been used to solubilize hydrophobic drugs, to increase blood circulation time, to obtain favorable biodistribution, and to lower interactions with the reticuloen-... 

Haag R. (2004) Supramolecular drug-delivery systems based on polymeric core-shell architecture. Angew Chem Int Ed 43 278-282... 

In addition to the benefits of MEF from metal nanostructures deposited onto solid supports that are very useful in surface bioassays, MEF can also be observed from individual nanostructures in bioassays carried out in solution. In this regard, fluorophores and metal nanostructures can be assembled in core-shell architecture and can be used as fluorescent nanoparticles as indicators in biological plications such as imaging of cellular activity or single-molecule sensing. 

Figure 3.2.6). Narrowly dispersed polystyrene (synthesized by atom transfer radical polymerization [polydispersity < 1.1]) was end fnnctionized with a phosphonate moiety that binds strongly to titanium oxide. The combination of narrowly dispersed titanium oxide and narrowly dispersed phosponate-terminated polystyrene generates a narrowly dispersed core-shell architecture as measured by dynamic light scattering, which can be spun into dielectric films. The covalent coating of polystyrene around titanium oxide is helpful at preventing aggregation of the nanoparticles in organic dispersion and in thin films.

Extrusion is a simple and low-cost process of encapsulation with core-shell architecture, which is able to preserve probiotic cell viability, owing to the limited use of harmful solvents and the small stresses exerted on microbial cells. However, its use on large scale is limited by the slow process of capsule fabrication. In contrast, owing to its easier scalability, fluid-bed coating is more widely used in the encapsulation of probiotic cells. 

With these considerations in mind, synthetic chemists have begun to address the needs of metal particle research by developing the synthetic chemistry of nanosized metals, with a view to using the strategies of molecular chemistry to prepare well-defined metal nanopartides. The goal may be stated as ... the search for synthetic methods for metal nanopartides of narrow size distribution and, if possible, with shape-control. Furthermore, bimetallic spedes will be considered, either with core-shell architecture or in alloyed form. 

In contrast to the prominent efforts to realize and use perfectly branched glycodendrons and glycodendrimers, a more moderate role can be assigned to hyperbranched glycopolymers (Fig. 5.23) and other highly branched derivatives (core-shell architectures, starlike stmctures, formation of defined aggregates/micelles). 

FIGURE 6.1 Formation and architecture of block copolymer micelles, which spontaneously form by self-assembly in water. The characteristic features are a pronounced core-shell architecture, which can be controlled by the individual polymer blocks. Typical examples for block copolymers are PEO-fc-PPO, PEO- -PCL, and PEO-fc-PAsp. Source Kataoka et al. [1], figure 1. Reproduced with permission of Elsevier. (See insert for color representation of the figure.)... 

D. Miyajima, F. Araoka, H. Takezoe, J. Kim, K. Kato, M. Takata, T. Aida, Ferroelectric columnar liquid crystal featuring confined polar groups within core-shell architecture. Science 336, 209-213 (2012)... 

Huang, M., Y. X. Zhang, F. Li et al. 2014. Merging of KirkendaU growth and Ostwald ripening Cu0 Mn02 core-shell architectures for asymmetric supercapacitors. Scientific Reports 4 4518. 

Micelles are composed of amphiphilic block copolymers that self-assemble into spherical shapes of nanometer diameter due to energy minimization with the surrounding solvent. When exposed to a hydrophilic solvent the hydrophilic domains orient toward the solvent, while the hydrophobic domains orient toward the core and form a clump away from the solvent. In a similar manner, when amphiphilic molecules are exposed to a hydrophobic solvent they form micelles with a hydrophobic block on the surface and a hydrophilic block in the core. Micelles thus have a unique core-shell architecture composed of either hydrophobic or hydrophilic blocks depending on the chemical structures and the medium. The hydrophobic or hydrophilic core provides a reservoir for water-soluble or insoluble drugs and protects them from decomposition in order to maintain activity and stability. Stearic acid (SA)-grafted chitosan oligosaccharide (CSO-SA) formed... 

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