Surfactant-inorganic interactions

Sayari et al [202,203] extended the LCT technique to the synthesis of mesostructured zirconium oxide. The use of long chain quaternary ammonium salts or primary amines as templates led to the formation of hexagonal and lamellar Zr02 phases, respectively. Zr(S04)2 was used as zirconium source, which provided a highly acidic medium, pH < 1.5. Consistent with the synthesis conditions and EDX analysis data a S X I mechanism where the surfactant-inorganic interaction is mediated by sulfate anions was proposed. Unfortunately, both structures collapsed upon removal of the surfactant either by high temperature calcination or by solvent extraction [203]. However, the hexagonal form was successfully... 

This classification is very useful especially for other types of surfactant-inorganic interactions such as those involving neutral surfactants as structure directors (templates). Such interactions can be denoted as follows ... 

S°I°, where both the surfactant (S°) and inorganic species (1°) are neutral. The surfactant-inorganic interaction is due to hydrogen bonding. 

Inorganic anions are the most common component in the synthesis which includes the counterion of inorganic precursor and surfactant, acid, base or salt additives. The acidic route is interesting in that it offers versatile structures and morphologies due to its weaker surfactant-silicate interaction in S + X —1+, which suggests that the presence of the counteranion is important for the acidic synthesis systems. 

I X S, where posithely surfactant molecules interact with positively charged inorganic oxide precursor, through a negatively charged mediator (X ). 

The (S 1+) route In this pathway anionic surfactants (S ) interact with cationic inorganic species (I+). 

Gas-to-particle conversion is an important secondary source of aerosol surfactants. Inorganic aerosols may acquire an organic component via in situ interactions with volatile organic compounds (VOCs), a family of processes... 

The coulombic surfactant-inorganic (S-I) interaction was the first interaction used in the synthesis of mesoporous MCM silica materials. Likewise, early efforts for the synthesis of mesoporous TM oxides utilized the coulombic interaction as the primary S-I interaction. In these studies, cetyltrimethylammonium bromide (CTABr) as a cationic surfectant and sodium dodecyl sulfate (SDS) as an anionic... 

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