Vesicle templating

The process utilizing supramolecular organization involves pore expansion in silicas. A schematic view of such micelles built from the pure surfactant and those involving in addition n-alkane is shown in Figure 4.9. Another example of pore creation provides a cross-linking polymerization of monomers within the surfactant bilayer [30]. As a result vesicle-templated hollow spheres are created. Dendrimers like that shown in Figure 4.10 exhibit some similarity to micellar structures and can host smaller molecules inside themselves [2c]. Divers functionalized dendrimers that are thought to present numerous prospective applications will be presented in Section 7.6. 

In the context of utilizing surfactant assemblies for building nanostructured polymeric materials, one other approach that deserves mention is the polymerization of standard monomers partitioned into the hydrophobic regions of surfactant aggregates one in particular that has received a lot of attention is vesicle templating [84]. The basic idea in this approach is to generate vesicles using appropriate surfactants and then to solubilize standard monomers, such as styrene, within the... 

An alternative to the polymerization o/vesicles with polymerizable surfactants is the polymerization in vesicles, or vesicle templating, in which a hydrophobic monomer swells the surfactant bilayer and is subsequently polymerized (Fig. 2b). In this case the vesicle is used like a mold that directs the polymerization process, and the surfactant molecules themselves are not incorporated into the final polymer. This is a transcriptive synthesis. The polymeric... 

Fig. 3. Polymer morphologies obtained by vesicle templating Hollow polymer spheres (top left) [24], parachutes (top right) [18], necklaces (bottom left) [17], and matrioshka structures (bottom right) [17], Adapted with permission from [17,18,24]...

Table 1. Experimental conditions for polymeric vesicle templating (e.g., the polymerization of monomers in vesicles)...

Fig. 4. Surfactants (top) and monomers (bottom) used for vesicle templating. See Table 1 for experimental conditions...

One of the exceptionally useful aspects of this group s work is not only the wide variety of monomers and polymerization conditions attempted but also the wide variety of characterization methods employed. Like Kaler et al., this group has characterized the initial surfactant vesicle template, the monomer-swollen vesicles, and the final polymeric product. Particular attention was paid to the effect of monomer and polymer on the surfactant bilayer properties. Cryo TEM experiments revealed subtle changes in the vesicle morphology, which were investigated further with micro DSC experiments [21]. 

Success in vesicle templating depends on control of reaction kinetics, monomer partitioning, membrane and polymer fluidity (Tg vs polymerization temperature), the use of cross-linking monomers, and anchoring polymerizable monomers. In practice, phase separation of the newly forming polymer and the surfactant bilayer has been observed under a variety of conditions. The extent of phase separation appears to follow intuitive guidelines, with the compatibility of the monomer and polymer with the surfactant of central importance. 

Figure 15 Vesicle template-directed self-assembly of a core-shell structure with ring-shaped polyoxometalates on the surface through electrostatic interactions between the cationic amphiphiles and the polyanionic ring.

Cuomo, F., Lopez, F., Miguel, M.G., Lindinan, B. Vesicle-templated layer-by-layer assembly for the production of nanocapsules. Langmuir 26, 10555-10560 (2010)... 

Vesicle-Templated Controlled Radical Polymerization An Alternative... 

Fig. 4 Synthesis of vesicle-templated nanocapsules by aqueous starve-feed emulsion polymerization using RAFT copolymers as stabilizers. Reproduced from [50] with permission from the American Chemical Society...

Ali SI, Heuts JPA, van Herk AM (2010) Controlled synthesis of polymeric nanocapsules by RAFT-based vesicle templating. Langmuir 26 7848-7858... 

Figure 4.6 Preparation of nanocapsules using a vesicle templating approach. (A) Sobdification in vesicles occurs in three steps ...

Nanocapsules (hollow nanoparticles, nanospheres) are submicrometric colloidal objects composed of a liquid core surrounded by a thin silicone shell. The vesicle templating, solidification in emulsion and solidification of vesicles are the main methods for preparation of the silicone nanocapsules. The vesicle templating method is based on imprinting in the prepared materials the shape and size of the vesicles used as a template. Among the most popular templates are vesicles created from phospholipids (liposomes), double-tailed... 

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