Bimodal meso-macropore structure

Several approaches towards the synthesis of hierarchical meso- and macro-porous materials have been described. For instance, a mixture that comprised a block co-polymer and polymer latex spheres was utilized to obtain large pore silicas with a bimodal pore size distribution [84]. Rather than pre-organizing latex spheres into an ordered structure they were instead mixed with block-copolymer precursor sols and the resulting structures were disordered. A similar approach that utilized a latex colloidal crystal template was used to assemble a macroporous crystal with amesoporous silica framework [67]. 

This method allows independent control over both the macropores, which are determined by the emulsion droplets in the first step of the process, and the mesopores, by the supramolecular self-assembly in the second step. Therefore, the two templating systems do not interfere vhth each other, and consequently the meso-and macro-structures can be optimized separately [21]. Inorganic oxides, such as silica, titania and zirconia, were obtained by this two-step process. The bimodal distribution of pores was characterized by highly ordered mesopores (5-10 nm) and by interconnected macropores (0.1 to 5 p,m). These materials possess high pore volumes (17 cm g ) and specific surface areas, as determined by the BET method applied to the nitrogen adsorption isotherm, of between 250 and 750 The... 

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