Full encapsulation

In an attempt to better understand the mechanism for encapsulation of cobaltocenium inside 46 we performed careful titrations of this redox-active cation with variable concentrations of host 4. To our surprise, we quickly realized that only 2-3 equivalents were necessary to fully shut down the electrochemical response of cobaltocenium.51 This result is in strong contrast to the NMR data, which clearly indicate a 6 1 [host/guest] stoichiometry for full encapsulation. There are two important differences between these two types of experiments. In the NMR experiments, solutions were prepared in pure, deuterated CD2CI2 and the only solutes present are cobaltocenium hexafluorophosphate (ca. 1 mM) and host 4 (0-8 mM). In the electrochemical experiments, solutions were prepared in isotopically unenriched CH2CI2 also containing 0.1 M tetradodecylammonium bromide as supporting electrolyte. The concentrations of cobaltocenium hexafluorophosphate and host 4 were similar to those used in the NMR experiments. It clearly became evident that the nature of the supporting electrolyte, especially the nature of its anion, was crucial to... 

The reason for different encapsulations is that the substations have been built over quite a long period of time, during which the technical solutions have improved fi om the wire fence solution to the full encapsulations. 

F = Full encapsulation, S = Semi-encapsulation, W = wire-fence encapsulation, E = Exposed operating environment, C = Clean operating environment... 

As shown in Figure 2.16, full encapsulation of the magnetite particles is obtained. 

A characteristic feature of cryptand complexes involving full encapsulation of a bound ion, such as frequently observed for cryptands of type 14, is the increased stability of the product complex relative to related monocycUc ligand complexes. In this context, it is noted that a variety of methods have been employed to measure host-guest... 

Substitution of the methyl groups in H2LI664 by 2-methylenepyridyl arms (H2LI674) provides conditions for full encapsulation of the metal ions, making these kinetically and thermodynamically more stable. Further condensation of the monometallic dialdehyde complex [Ma(L1674)] with 1,3-diaminopropane (1,3-pn) in the presence of H+ affords the macrocyclic product (M(L1675)] (Eq. 8.11). 

Figure 14.5 Full-encapsulation cross-section. After Koemer and Hwu (1989).

Using a method halfway between simple electrostatic condensation and full encapsulation with neutral polymers as described above, a new delivery vehicle called a PIC micelle was developed [54, 128]. When a block copolymer with a neutral... 

The possible morphologies that can be created during the sonication process are depicted in Figure 10.1. There are two thermodynamically stable cases regarding the clay location, namely the preferential location at the droplet surface (Figure lO.le) and full encapsulation (Figure 10.1a). The first case is desirable when solid particles instead of surfactant molecules are used to stabilize a (mini)emulsion and one speaks of a Pickering (mini)emul-sion. The latter case of encapsulation of clay platelets into the latex particles is preferred when surfactant molecules are used to stabilize the (mini)emulsion. 

Figure 10.1 Schematic illustration of the miniemulsion process and the possible morphologies of polymer-clay droplets/particles during the miniemulsification step and miniemulsion polymerization (a) full encapsulated morphology (b) dumbbell-like or snowman-like morphology (c), (d) dispersed silicate platelets with miniemulsion droplets or polymer adsorbed to its surface (e) clay platelets acting at the surfaces of droplets/particles.

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