Raspberry shape

Armes and coworkers studied the preparation of polypyrrole particles in the presence of silica sols [48, 49]. Hydrogen bonding between the silica surface and the polypyrrole particles, in addition to electrostatic and hydrophobic interactions, led to raspberry-shaped nanocomposite colloids. 

Other studies investigated the incorporation of active molecules without a functionalization step. For example, supercritical CO2 was employed to impregnate the core of the PNBE-PEO particles with salicylic acid [35, 36]. Another variation consisted of adding a di-norbornenyl molecule 19 (Scheme 2.6) to the monomer-macromonomer mixture to obtain cross-linked nanoparticles by dispersion ROMP [37]. Reticulated polymer particles are interesting nanocarriers for the controlled release of encapsulated active substances. Raspberry-shaped nanoparticles in the size range of 300-600 nm were obtained, which arose from a double nucleation mechanism. NBE and the cross-linker were rapidly copolymerized in the first minutes of the reaction to afford a first population of highly cross-fiked particles, thereby preventing the incorporation of new active chains inside. A second population of particles was created subsequently from the... 

Agglomerates formed by coalescence and by layering can usually be distinguished by their appearance. Layered granules tend to a smooth spherical shape and examination of their interior cross sections reveals a layered onion skin construction. Coalesced granules tend to a more irregular spheroidal shape and often exhibit a rough raspberry -type surface. 

Well-ordered, raspberry-like assemblies of cholesterol-bearing PuL (CHP) particles were prepared by Michael addition of acrylate-group-modified CHP nanogels with four-arm star-shaped PEG bearing thiol groups at the terminus (PEGSH Fig. 3) [79],... 

Common cultivated raspberries often have nice shape and colour, but their taste is just watery and acidic. Fragrant raspberries develop a delicious fresh, fruity, green, floral, violet like perfume with some seedy, woody background. Ripe raspberries are sweet and very juicy. 

Cloudberries have the same shape as raspberries, but a different, yellow-orange colour. The taste is completely different no fresh, fruity and violet character, but sour, fruity, juicy, aromatic spicy in the direction of cinnamon, clove. 

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. 

Of relevance to this section, Reculusa et al. also recently demonstrated that the addition of a small amount (only 1.5 pmole/m ) of a monomethylether mono methylmethacrylate poly(ethylene oxide) macromonomer (structure 9, Table 4.5) allowed the direct self-assembly of nanometric polystyrene latex particles on the surface of submicronic sihca particles through an in-situ nucleation and growth process (Fig. 4.12) [102]. The two sets of particles were assembled in a raspberry-like morphology via the formation of hydrogen bonds at the interface of the inorganic and organic coUoids. The size and shape of the assembly can be easily controlled by varying the sizes and stoichiometries of the colloidal components (Fig. 4.13). 

Microscopic observations revealed that polymer formed during the above-mentioned process was shaped into the raspberry-like particles (see Figure 2). The diameters of particles formed in the absence of poly( ethylene oxide) were in the range of 25-100 jm, whereas the diameters of particles formed by polymerization in the presence of poly(ethylene oxide) (samples with Mn equal to 15 000 and 40 000 were used in the studies)... 

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