Initial surfactant templating mechanism

Formation Mechanism from Initial Surfactant Templating Mechanism to Final Self-Formation Procedure... 

This may be explained as follows the SDS interacts with the maximum of partially protonated aminopropyl groups, by electrostatic interactions between dodecylsulfate anion and and sodium cation neutralization. The remaining amino groups are entrapped into the silica network. The amount of P-CD moieties incorporated depend on the initial molar ratio of P-CD APS, and not of the presence or not of SDS. P-CD groups may not interact with SDS. We can say, that for these hybrid materials, the templated mechanism is a S P one (S for anionic surfactant, P for cationic aminosilica species). 

Miniemulsion systems are somewhere in between macro- and microsystems. They contain both micelles and monomer droplets, but the monomer droplets are smaller than in macrosystems [134-137]. For both micro- and minireaction systems in which the initiator is soluble in the continuous phase, the mechanism for polymerization is determined by the relative surface areas of micelles versus monomer droplets. Compared with the miniemulsion (5-10wt% of surfactant used), high concentration (15-30 wt%) of smfactant forms robust and compact micelle, and the inner space of micelle can be used as a nanoreactor. Besides sphere and layer morphologies, a wide range of morphological spectra could be obtained by carefully controlling the synthetic conditions. The surfactant templates for sphere, rod, and layer nanomaterials are schematically represented in Scheme 5. 

The initial templates for the M41S family materials are quaternary ammonium surfactants with positive charge and long tail (hydrocarbon chain). The synthesis was believed to proceed via the formation of a lyotropic liquid crystal, which is an ordered assembly of micelles (details will be discussed in the mechanism section). The... 

The three major routes are (i) true liquid crystal templating at high surfactant concentrations, which is used for the formation of monoliths, thick layers or, via electrodeposition techniques, formation of thin films (ii) cooperative self assembly at surfactant concentrations where micelles are present in solution, which can be used to make powders (with either well-defined particle shapes or random structures), fibres and thin films grown at interfaces from solution and (iii) EISA at very low surfactant concentrations, where no micelles are initially present in solution, and solutions are in general prepared in nonaqueous solvents. This route is used to prepare thin films by dip or spin coating and powders via aerosol routes. The following sections will look at the current understanding of the mechanisms involved in each route to mesoporous materials. 

A highly porous polymeric foam can be prepared through emulsion templating by polymerizing the continuous phase of high internal phase emulsions [150], A maleimide-terminated aryl ether sulfone oligomer was copolymerized with divinylbenzene in the continuous phase, using a mixed surfactants system, cetyltrimethylammonium bromide, dodecylbenzene-sulfonic acid sodium salt, and a peroxide initiator. The polymers show a CO2 adsorption and improved mechanical properties. The materials exhibit an open cell and a secondary pore structure with surface areas of a 400 m g ... 

Microemulsions [191, 192] are transparent, optically isotropic and thermodynamically stable liquids. They contain dispersion of polar and nonpolar solvent, usually water or aqueous solutions and oils. Adding surfactants stabilizes droplets of 1-100 nm in size. Due to amphiphilic properties of the surface active substances containing lipophilic groups and one or two lyophobic C-H chains mainly collected at the interface of two liquid phases, they cannot be mixed under normal conditions. Unlike traditional macroemulsion, which is kinetically stabilized only by the external mechanical energy supply, nano-domains in the microemulsions are formed spontaneously. Their size depends on the microemulsion composition, temperature and elastic properties of the separating film of surfactant. In particular, in the case of water-oil microemulsions with spherical nanosized micelles of water dispersed in oil, water droplets can be used as nanoreactors and templates for the solid nanoparticles fabrication. Since the reaction is initiated by the spatially restricted water and micelle, heterogeneous nucleation and crystal growth can be controlled. 

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