Hierarchically ordered spherical approach

Vast tabulations of 13C chemical shift data have been assembled in computer searchable form. These databases form the basis for 13C chemical shift prediction algorithms. For the most part, carbon chemical shifts can be calculated using what is referred to as a Hierarchically Ordered Spherical Environment (HOSE) code approach [28]. To calculate a given carbon s chemical shift, the influence of each successive spherical shell is applied to the starting chemical shift for that carbon to calculate its overall chemical shift. Typically, programs will calculate shifts for 3 or 4 layers, beyond which the effects of most substituents are negligible. The spherical layers surrounding the 23-position of strychnine are shown in Fig. 10.8. 

The materials which have been mentioned here so far are predominantly shaped in planar films of hierarchical order. However, the synthesis of hierarchically structured particles is also highly desirable, as they might be further processed and used for the preparation of composite porous materials. Wu et al. showed the synthesis of raspberry-like hollow silica spheres with a hierarchically structured, porous shell, using individual PS particles as sacrificial template [134]. In another intriguing approach by Li et al. [135], mesoporous cubes and near-spherical particles (Fig. 10) were formed by controlled disassembly of a hierarchically structured colloidal crystal, which itself was fabricated via PMMA latex and nonionic surfactant templating. The two different particle types concurrently generated by this method derive from the shape of the octahedral and tetrahedral voids, which are present in the template crystal with fee lattice symmetry. 

Jenekhe and coworkers showed that solution-cast micellar PPQ-Z -PS films consisted of multilayers with the hexagonally ordered arrays of spherical holes (Jenekhe and Chen, 1998, 1999). The hierarchical self-assembly approach to the microporous solids with a hollow core, a... 

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