Pseudomorphic transformation of pre-shaped silica beads into MCM-41 and MCM-48 is introduced as a new versatile procedure to independently control and finely tune the textural characteristics of advanced high-performance chromatographic supports at nano-and micrometer scale.The reaction takes place in the intergranular porosity of the parent silica-gel particle which acts as a nanoreactor.Because the resulting hybrid mesophase is metastable in its synthesis medium,the kinetics of each of the elementary steps-diffusion of hydroxide and surfactant,dissolution of parent silica,self-assembly,condensation of the new silica network-must be precisely controlled.In the paper examples are given of the preparation of discrete homodisperse spherical particles of MCM-41 and MCM-48,with pore sizes in the range 4 to 9 nm,form different silica sources.
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