Mercaptopropyl silica grafting

The textural properties govern the diffusion process so that a well-defined structure may facilitate diffusion-controlled reactions. For example, the adsorption of heavy-metal ions (Hg + and Cu ) reveals a dramatic discrepancy between ordered and disordered mesoporous silica grafted with the aminopropyl or mercaptopropyl group [55]. The ordered mesostructure with a mean pore size of 6.5 nm brings about complete accessibOity of the functional groups. While... 

Because the grafting techniques described in Section 3.5.1.2 lead to rather low loading, it is of interest to incorporate functional groups directly and in large amounts into a material via a sol-gel process. Open and patent literature report colloidal silicas [23], aerogels [24] and xerogels [14] with 3-mercaptopropyl, 2-phenylethyl, or benzyl functional groups. These materials are valuable precursors to sulfonated polysiloxanes (Section 3.3). 

In this entry, several kinds of comb-shaped polymers with highly ordered side chains have been introduced as attractive organic phases for RP-HPLC. Poly(octadecyl acrylate), ODA , is one of the simplest comb-shaped polymers, and its grafting for introduction onto silica surface is done by a one-step telomerization with 3-mercaptopropyl trimethoxysilane followed by immobilization with the terminal trimethoxysilyl group grafting-to method). The chromatographic results are summarized as follows ... 

Also, the vinyl-grafted FDU-1 and mercaptopropyl-grafted SBA-15 were prepared by post-synthesis modification (m) of the corresponding silicas with VS and MPS, respectively, similarly to the procedure used for the post-synthesis modification reported elsewhere [2, 8-9]. The resulting samples were denoted as FDU-lVm and SBA-15Sm, where m stands for the post-synthesis modification. 

Ordered mesoporous silica containing triazine moieties (Figure 3), based on the SBA-15 structure, has also been reported as an efficient and a reusable catalyst for the synthesis of chromenes 20 xmder solvent-free reaction conditions (Scheme 12) [75]. The catalyst was prepared from 3-mercaptopropyl-grafted SBA-15 by thiol-ene click reaction with 2,4,6-triallyloxy-l,3,5-triazine. The characterization data of the solid demonstrated the total disappearance of C=C bonds in triazine moiety. This feature strongly suggested the formation of bridges between the triazine and the mesopore walls. 

Fig. 16.15 Comparison between thiol-fiinctionalized silica gels and ordered mesoporous silicas (MCM-41 and SBA-15 types) in CPEs applied to preconcentration electroanalysis of Mg species electrochemical curves obtained after 2 min accumulation in 1 pM Hg , with various mercaptopropyl-grafted silica samples incorporated in carbon paste electrodes, (a) small pore ( 4 nm) silica gel, (b) large pore ( 6 nm) silica gel, (c) small pore ( 3 nm) MCM-41, and (d) large pore ( 6 nm) SBA-15. The curves were recorded after transfer to an analyte-free electrolyte solution (5 % thiourea in 0.1 M HCl), by applying anodic stripping voltammetry in the differential pulse mode. Reprinted with permission from reference (734) Copyright (2003) Wiley-VCH...

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