Hybrid surfactants synthesis

Fig. 2.8 Synthesis of hybrid surfactants. (Reproduced with permission from Ref. 149. Copyright 1992 by the American Chemical Society.)...

The hybrid surfactants synthesized by Yoshino et al. [150] contain an aromatic ring. The synthesis involves the following sequence of reactions shown in Fig. 2.9. The hydrophile is a sulfonate attached to the molecule through a —CSOsNa bond, which is stable to hydrolysis. 

In this research study an ordered, mesoporous hybrid organosilica material incorporating a biphei rl moiety was fabricated. The polymerization process was surfactant-mediated to ensure uniform pore pattern and narrow pore size distribution. The synthesis of the organosilica precursor was done and investigated by the research group of the Inorganic Synthesis and Computational Research Laboratory of Institute of Chemistry, Diliman, Quezon City. 

Synthesis of Hybrid Silica Materials Using an Anionic Surfactant... 

The synthesis was the same as the one presented above but without the use of surfactant. TEOS was added to a P-CDAPS solution (in a water-ethanol mixture with molar ratio 9 1) in varying proportions. The resulting mixture was stirred Ih at ambient temperature and then kept statically for 2 days at 373 K. The precipitate obtained was hltered and the powder dried under vacuum at 333 K. The initial molar composition was 0.5 TEOS x P-CDAPS 180 H O 20 EtOH where x is equal to 0.5, 0.25 or 0.1. The obtained hybrid silica materials were designated Tbn, where n= 1, 2 and 3 corresponds to x = 0.5, 0.25 and 0.1 respectively. 

In 2002, Chiang and coworkers[124] developed a new scheme for the confined synthesis of TPA-silicalite nanocrystals. The surfactant cetyltinmethylammonium bromide (CTAMeBr) (in ethanol solution) was added to the single- and double-heated TPA-silicalite precursor sols (SHPS and DHPS), and the mixture was flocculated at a certain pH value to collect the nano-size silicate species in the precursors, and then dried. The dried precursor/surfactant hybrid was pressed into pellets and then steamed in a stainless steel autoclave at 110 150°C for 7 36 h. Finally, the product was calcined to remove the surfactants and TPA. The particle sizes of silicalite-1 produced in this method are about 30 nm. The study indicates that the nanoparticles collected by surfactants already exhibit the structural features of MFI. They crystallize entirely to form silicalite-1 nanocrystals after steam treatment at 110 150 °C. This new solid-phase approach provides a way to synthesize MFI nanocrystals without the problem of separation and collecting nanocrystals from suspension, and it also avoids the large consumption and cost of special mesoporous templates used in the confined-synthesis methods. 

As a new example of SI covalent synthesis pathway, siloxane oligomers with alkoxy functionality and covalently attached alkyl chains were used as both silica source and surfactant for the synthesis of ordered silica-organic hybrids without the use of an additional template.[60]... 

Fig. 4 Ligand assisted templating mechanism for the synthesis of niobium oxide. The amine surfactant forms covalent bonds with the niobium (V) ethoxide, resulting in the formation of a hybrid interface. Upon exposure to water, the system organizes into various structures such as bidimensional hexagonal (Nb-TMSl), three-dimensional hexagonal (Nb-TMS2), lamellar (Nb-TMS4), or a cubic phase. (Nb-TMS3 is not shown in the figure.) (From Ref...

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