Hard-particle methods surfactants

To better control the ordering of mesopores in the silica shell, along with particle size and shape, the hard template method in combination with surfactant templating has been studied intensively. Typically, hollow particles with hexagonally ordered mesoporous shells can be obtained by using PS beads and CTAB in an aqueous ammonia solution. After the growth of a silica-surfactant meso-structured composite shell on the surfeice, the PS template is finally removed by calcination to form hollow spheres. Several reports have succeeded in... 

The polymerization reaction takes place in the bulk and the formation of discrete particles is a result of the good solubility of the monomer in the solvent and the low solubility of formed particles of a certain size. Because this approach is dependent on the existence of such a kind of a solubility/non-solubility regime for the monomer, crosslinker, template, and polymer network, it might be hard to find the correct combination of compounds needed to interact in the prescribed way. Additionally, there is a high risk of coagulation with this method as no surfactant is added for the stabilization of the interface between the formed polymer and the monomer containing solution. 

The extent of adsorption of eommereial surfaetants developed for use in reservoir recovery proeesses ean vary from near zero to as high as 2.5 mg/g. Surfactant adsorption on rock surfaces is usually measured by either static (batch) or dynamic (coreflood) experiments. The static adsorption method, employing crushed rock samples, is essentially the classical method for determining adsorption isotherms at the aqueous solution/solid interface and involves batch equilibrations of particles in solutions of different initial surfactant concentration. The dynamic coreflood method is more involved but employs a greater solid to liquid ratio and is therefore more sensitive, see references [J69-J7J]. Temperature, brine salinity and hardness, solution pH, rock type, wettability, and the presence of a residual oil phase have all been found to influence the extent of adsorption of different surfactants [116,152,172],... 

The hard-templating growth methods described before should not be confused, on the contrary, with soft-templating approaches which usually are accomplished in solution phase in the presence of free surfactant molecules which severely attend the nucleation of a new particle and the further shape development selectively and dynamically interacting with the evolving particle surface facets. 

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