Novel 3‐hydroxypropyl‐bonded phase by direct hydrosilylation of allyl alcohol on amorphous hydride silica

Abstract

A novel 3-hydroxypropyl (propanol) bonded silica phase has been prepared by hydrosilylation of allyl alcohol on a hydride silica intermediate, in the presence of platinum (0)-divinyltetramethyldisiloxane (Karstedt's catalyst). The regio-selectivity of this synthetic approach had been correctly predicted by previous reports involving octakis(dimethylsiloxy)octasilsesquioxane (Q8M8H) and hydrogen silsesquioxane (T8H8), as molecular analogs of hydride amorphous silica. Thus, C-silylation predominated (~ 94%) over O-silylation, and high surface coverages of propanol groups (5±1 µmol/m2) were typically obtained in this work. The propanol-bonded phase was characterized by spectroscopic (IR and solid state NMR on silica microparticles), contact angle (on fused-silica wafers) and CE (on fused-silica tubes) techniques. CE studies of the migration behavior of pyridine, caffeine, tris(2,2’-bipyridine)Ru(II) chloride and lysozyme on propanol-modified capillaries were carried out. The adsorption properties of these select silanol-sensitive solutes were compared to those on the unmodified and hydride-modified tubes. It was found that hydrolysis of the SiH species underlying the immobilized propanol moieties leads mainly to strong ion-exchange based interactions with the basic solutes at pH 4, particularly with lysozyme. Interestingly, and in agreement with water contact angle and electroosmotic mobility figures, the silanol-probe interactions on the buffer-exposed (hydrolyzed) hydride surface are quite different from those of the original unmodified tube.

Neutral hydrophilic coatings for capillary electrophoresis prepared by controlled radical polymerization

“…The first step is based on the formation of a stable Si–C bond by the catalytic addition of silicon hydride to an olefin (hydrosilylation). We have recently demonstrated that allyl alcohol can also be anchored to the hydride silica surface and that it does so with a high coverage (3–5 μmol m −2 ) (29). In the esterification of the anchored alcohol groups with α-bromoisobutyryl bromide, we found that using DMF as solvent and pyridine as HBr-binding base maximize the solubilization of the bromide salts produced during the esterification process.…”

“…Hydride silica substrates were prepared as described previously (28). 3-hydroxypropyl (propanol) bonded silica phase was prepared by hydrosilylation of allyl alcohol on hydride silica, as described in a recent report (29). Esterification of the bound propanol groups was carried out by treatment for 6 h at room temperature (20 ± 2 °C) with a solution containing 0.25 M of α-bromoisobutyryl bromide and 0.25 M of pyridine in dry DMF under a nitrogen blanket (30–32).…”

Sequential Functionalization of a Natural Crosslinker Leads to Designer Silicone Networks

“…The platinum‐catalyzed reaction (typically Speier's or Karstedt's catalyst) with SiH groups can also set up a competition between the desired reaction at the allyl groups (e.g., Scheme B) and at the phenol, to give SiOPh+ H 2 . The latter reaction has been reported to occur much more slowly than the former, and that outcome was observed here too. Clean hydrosilylation occurred without change in the phenol concentration.…”