Grafting covalent

In a related approach, alginate beads were modified with aminopropyl-silicate membrane (derived from APTS and tetramethoxysilane). The amino groups remaining on the surface are favorable for the anchoring of biomolecules [84], 

In comparison to the other immobilization methods, this process is disadvantageous since generally the support must be modified which is time consuming and 

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Fig. 4. Data of Auroy et al. [25] on polydimethyl-siloxane chains covalently grafted in the interior of a silica porous medium. L is the measured layer thickness from neutron scattering d is the average spacing per chain from the grafting density. The format of the plot is suggested by Eq. 5. The linearity of that relation is seen in these data...

Glos and Reiser [23] introduced aza-bis(oxazolines) as new chiral ligands for copper and palladium catalysts. Because of the structural flexibility of these compounds they also prepared an immobilized ligand by covalent grafting to methoxypoly(ethyleneglycol) (structures 14 and 15 in Scheme 9). 

These N,N-chelating hgands were then covalently grafted on a modified Y-zeolite containing supermicropores . The selectivities observed were low (up to 11% ee) but led to similar values when comparing the imsupported and zeolite-supported Cu complexes. Interestingly, however, the zeolite catalysts could be recovered and reused several times with no loss of activity. 

Rechavi and Lemaire reported the heterogeneization of copper bis(oxa-zoline) catalysts through covalent grafting onto silica via functionalization of indaBOX ligand by triethoxysilane groups [117] (84 in Scheme 47). 

Interesting results have been presented by Baleizao et al. for chiral vanadyl Schiff base complex [50].120 The 29Si MAS NMR spectra have confirmed covalent grafting of the vanadyl complex into the silicate skeleton. 

A more sophisticated method was developed by Ren et al. [123] for the immobilization of penicillin G acylase by covalent grafting in the interlayer galleries of a LDH by a three-step procedure using a glutamate pillared LDH as the starting material. 

The approach precludes the usage of volatile organic solvents, is relatively much faster, efficient, and eco-friendly. Significant rate enhancements are reported in the 1,3-dipolar cycloaddition reactions including the use of covalently grafted dipolaro-philes on the ionic liquids [189]. 

Previous work [111] by our group has demonstrated that RTIL-catalyzed 1,3-dipolar cycloaddition under the action of microwave irradiation leads to dramatically shorter reaction times with better yields of isolated products. We have recently investigated the reactivity of the formyl group covalently grafted on the ionic liquid phase 75 in the Knoevenagel reaction with malonic derivatives 76 [112], as shown in Scheme 8.76. 

For some soft particles effective anchoring may require covalent grafting of the incompatible PS blocks to the core polymer. 

Fig. 5.9 Covalent grafting of (a) linear polymer and (b) dendrimer-like hyperbranched polymer of azo-functional porphyrin groups from alkyne functionalized CNTs. Redrawn from [122].

Sebe, G. and Brook, M. (2001). Hydrophobization of wood surfaces covalent grafting of silicone polymers. Wood Science and Technology, 35(3), 269-282. 

As discussed in the previous section, perfluorinated polyether pony-tails can be covalently grafted onto PPI dendrimers, and it has previously been shown that such materials are soluble in liquid CO2 [17]. HRTEM confirms that particles prepared within such dendrimer templates are nearly mono-disperse and are of a size that is consistent with the dendrimer template (Sect. 2.5.4). Such dendrimer-encapsulated metal particles are quite soluble in liquid and SC CO2. 

Irregularly hyperbranched grafts provide a useful way to modify surfaces. A variety of chemistry can be used and a wide variety of grafts can be prepared. The hyperbranched grafts can serve as supported membranes, as catalyst supports or as substrates for further covalent graft chemistry. Functional groups within these interfaces can be readily modified by solution-state chemistry. The interfaces themselves can be used as media for further chemistry within the interface or as substrates in molecular recognition and self assembly of other macromolecules. 

Cooper et al. [153] synthesized a series of PTMO-based polyetherurethane (PEU) containing covalently grafted GRGDSY-, GRGDVY- and GRGESY-peptides. Their synthetic route is as follows ... 

Au NPs protected with a thermo-responsive polymer such as PNIPAM by the covalent grafting to technique with different end-functional PNIPAMs and various ratios between PNIPAM and HAuC14 has been studied. PNIPAM samples were synthesized through either conventional radical polymerization or living/controlled radical polymerization. With this approach, very small and quite monodisperse Au NPs are obtained with diameters ranging from 1.5 to 2.3 nm [94]. 

Figure 4. Diffuse reflectance UV/vis spectra of MCM-41 a) with adsorbed rhodamine dye (0.0075-mmol/g MCM-41), b) with covalently grafted rhodamine dye (0.01 m mol/g MCM-41 0.5 mmol APTES/g MCM-41) compared to rhodamine B sulfonylchloride c) in ethanol and d) in water.

Two techniques were used to measure the apparent covalent grafting a Soxhlet extraction and an elution extraction. The Soxhlet procedure is well known. The elution procedure involved placing the graft... 

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