Isocyanatopropyl triethoxysilane

Chitosan membranes can also be superficially modified, for instance with 3-isocyanatopropyl triethoxysilane. Silanol groups and calcium salt acted as nucleation sites and accelerator, respectively, for the formation of apatite crystals therefore, this chitosan membrane is a bioactive guided bone-regeneration material thanks to its apatite-forming ability [341]. 

End-capping of both ends of a,co-hydroxyl PCL with 3-isocyanatopropyl triethoxysilane (IPTS). 

Saka and Yakake (1993) chemically modified wood samples with 3-isocyanatopropyl-triethoxysilane (IPTES) (Figure 7.9c). Wood was impregnated with acetone solutions of IPTES of different concentrations. Where the wood had been pre-swollen by treating with pyridine vaponr, a maximnm WPG of 27 % was obtained, whereas without pre-swelling of the cell wall a WPG of only 7 % was obtained. Pyridine also serves as a catalyst for the reaction of isocyanate with wood. SEM-EDXA showed the presence of silicon in the cell walls of the treated wood. Becanse of the lower WPG obtained without cell wall swelling, ASEs of the order of 20 % were obtained, compared to about 60 % when swelling of the cell wall was used prior to reaction. 

It is also worthwhile to outline at this place the immobilization procedure that was used for the preparation of type I CSPs A bifunctional linker with a terminal isocyanate on one side and a triethoxysilyl group on the other end (3-isocyanatopropyl triethoxysilane) was reacted with the native cinchona alkaloids quinine and quinidine and subsequently the resultant carbamate derivative in a second step with silica [30], Remaining silanols have been capped with silane reagents, yet, are less detrimental for acidic solutes because of the repulsive nature of such electrostatic interactions. CSPs prepared in such a way lack the hydrophobic basic layer of the thiol-silica-based CSPs mentioned earlier, which may be advantageous for the separation of certain analytes. 

In a typical reaction, the macrocycle is treated with a 2-3 M excess of (3-isocyanatopropyl)triethoxysilane in dry DMF. The derivative is then added to a dry DMF slurry of silica gel ( 2 g of functionalized selector to 4 g of silica gel). The solution is stirred, allowed to react for 20 h at 107°C, and then cooled, filtered, and washed with methanol, 50% aqueous methanol, and methanol again, and finally dried. Surface coverage data are reported only in the case of the commercially available vancomycin CSP (see Table 2.2), immobilized by joining on average three linkers per vancomycin molecule, probably via a 3-isocyanatopropyl-silane [48]. 

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