Core-shell molecules

After the initial reports on dendritic molecules [19], proposals have been made for the construction and applications of guest-host systems made out of dendrimers [1,2,35]. The concept of topological trapping by core-shell molecules is based on... 

At the nanoscale dimensional level it was shown by Hirsch et al. [276] that [60]-fullerenes could be used as a core tecton to construct a core-shell molecule with 7b-symmetrical Ceo core and an extraordinarily high branching multiplicity of 12. 

Uppuluri S, Swanson DR, Brothers HMII, Piehler LT, Li J, Meier DJ, Hagnauer GL, Tomalia DA (1999) Teclo(dendrimer) core-shell molecules macromolecular tectonics for the systematic synthesis of larger controlled structure molecules. Polym Mater Sci Eng (ACS) 80 55-56... 

More recently Frechet and Gitsov [130] used a similar approach as above and synthesized a novel series of dendritic copolymers derived from a central penta-erythritol core unit. These hybrid star molecules behaved as unimolecular micelles with different core-shell conformational-structures as a response to the polarity of the solvent used. 

Fig. 18 Phase space of PI-fc-PS-fc-PEO in vicinity of ODT. Filled and open circles-. ordered and disordered states, respectively, within experimental temperature range 100 < T/° C< 225. Outlined areas compositions with two- and three-domain lamellae (identified by sketches) shaded regions three network phases, core-shell double gyroid (Q230), orthorhombic (O70), and alternating gyroid (Q214). Overlap of latter two phase boundaries indicates high- and low-temperature occurrence, respectively, of each phase. Dashed line condition tfin = 0peo associated with symmetric PI-fc-PS-fc-PEO molecules. From [75]. Copyright 2004 American Chemical Society...

Hu Y, Litwin T, Nagaraja AR et al (2007) Cytosolic delivery of membrane-impermeable molecules in dendritic cells using pH-responsive core-shell nanoparticles. Nano Lett 7 3056-3064... 

Thus, there are two limitations of the pycnometric technique mentioned possible adsorption of guest molecules and a molecular sieving effect. It is noteworthy that some PSs, e.g., with a core-shell structure, can include some void volume that can be inaccessible to the guest molecules. In this case, the measured excluded volume will be the sum of the true volume of the solid phase and the volume of inaccessible pores. One should not absolutely equalize the true density and the density measured by a pycnometric technique (the pycnometric density) because of the three factors mentioned earlier. Conventionally, presenting the results of measurements one should define the conditions of a pycnometric experiment (at least the type of guest and temperature). For example, the definition p shows that the density was measured at 298 K using helium as a probe gas. Unfortunately, use of He as a pycnometric fluid is not a panacea since adsorption of He cannot be absolutely excluded by some PSs (e.g., carbons) even at 293 K (see van der Plas in Ref. [2]). Nevertheless, in most practically important cases the values of the true and pycnometric densities are very close [2,7],... 

Figure 12.20 Schematic representation of a core-shell tecto-(dendrimer) molecule in solution...

Tomalia et al. reported that the surface amines of PAM AM dendrimer can successfully react with methyl esters of other PAMAM dendrimers to afford core-shell tecto-(dendrimer) molecules [65]. Furthermore, they also reported the synthesis of rod-shaped cylindrical dendronized polymers from poly(ethyleneimine) cores without any crosslinking, albeit with the use of excess reagents [58]. These reports lead us to propose a new approach toward hybridized dendrimers and polymers (path C, Figure 15.3). As shown in Scheme 12,... 

Fig. 7 The interaction and coupling modes of dye molecules and metal in a core-shell structure for fluorescence enhancement...

Various novel imprinting techniques have also been presented recently. For instance, latex particles surfaces were imprinted with a cholesterol derivative in a core-shell emulsion polymerization. This was performed in a two-step procedure starting with polymerizing DVB over a polystyrene core followed by a second polymerization with a vinyl surfactant and a surfactant/cholesterol-hybrid molecule as monomer and template, respectively. The submicrometer particles did bind cholesterol in a mixture of 2-propanol (60%) and water [134]. Also new is a technique for the orientated immobilization of templates on silica surfaces [ 135]. Molecular imprinting was performed in this case by generating a polymer covering the silica as well as templates. This step was followed by the dissolution of the silica support with hydrofluoric acid. Theophylline selective MIP were obtained. 

Another approach of this kind uses the approximate Brueckner orbitals from a so-called Brueckner doubles, coupled-cluster calculation [39, 40]. Methods of this kind are distinguished by their versatility and have been applied to valence ionization energies of closed-shell molecules, electron detachment energies of highly correlated anions, core ionization... 

Highly monodisperse CdSe/CdS core/shell nanoparticles have been prepared by thermolysis in tri-n-octylphosphine oxide (TOPO) using [Cd(Se2CNMe( Hex))2] (250 °C for 30 min) and [Cd(S2CNMe( Hex))2] (250 °C for 30 min) as single-molecule precursors in a one-pot synthesis [118,119]. [Cd(Se2CNMe(Hex))2] (0.8 g) was dissolved in trioctylphos-... 

A similar increase in the values for the hyperfine constants and parameters of the P,T-odd interactions when the correlations with the core shells (primarily, 5s, bp) are taken into account is also observed for the BaF molecule [93], as one can see in Table 3. Of course, the corrections from the 4/-electron excitations are not required for this molecule. The enhancement factor for the P,T-odd effects in BaF is three times smaller than in YbF mainly because of the smaller nuclear charge of Ba. 

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