SPB1 and SPB1,2: Synthesis and Determination of the Microstructure and Physical Properties

New nano-structures of silica namely SPB particles (silica mesoporous particles, prepared by sol-gel method using triblock copolymers as template) were successfully synthesized, in water/n-octane (co-solvent) system and acidic media. Tetraethoxysilane (TEOS) as silica precursor, ethanol as co-surfactant and mixture of two copolymers of PPG-b-PEG-b-PPG and PEG-b-PPG-b-PEG (Pluronic) as template were used. The prepared new mesoporous silica particles were characterized using nitrogen adsorption-desorption (BET), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analyses. The obtained results indicated that the porosity of mesoporous materials and their surface properties could be improved by using a mixture of two copolymers as template. Also mixed triblock copolymers could adjust the pore size distribution of the mesoporous silica particles to a normal distribution. As confirmed by BET analysis, the mean pore diameters of SPB1 and SPB1,2 silica particles were found to be 5.48 nm and 3.21 nm respectively. The specific surface area and pore volume for SPB1,2 silica particles also increased with mixed block copolymers (SBET= 632.36 m²/g, VP= 0.342 cm³/g) compared to SPB1 particles (SBET = 577.27 m²/g, VP= 0.231 cm³/g). SEM results confirmed that the structures of these samples were spherical. Furthermore, the results also revealed that elimination of n-octane co-solvent from the reaction produced non-uniform large aggregates where the shape of particles changed from the spherical to non-spherical porous particles. These results showed that using a mixture of two triblock copolymers as template have outstanding effect on porosity, specific surface area, morphology, and microstructure of the new mesoporous silica particles.