Triblock Copolymer Syntheses of Mesoporous Silica with Periodic 50 to 300 Angstrom Pores

TLDR

SBA‑15 is synthesized in acidic media at 35–80 °C using poly(alkylene oxide) triblock copolymers and optional cosolvents, producing highly ordered hexagonal mesophases that can be fabricated over a wide range of pore sizes and wall thicknesses and whose block copolymer templates can be recovered by ethanol extraction or mild heating. The resulting SBA‑15 materials exhibit uniform hexagonal pores up to ~300 Å, interlattice spacings of 74.5–320 Å, pore volumes up to 0.85, wall thicknesses of 31–64 Å, and remain thermally stable in boiling water after calcination at 500 °C.

Abstract

Use of amphiphilic triblock copolymers to direct the organization of polymerizing silica species has resulted in the preparation of well-ordered hexagonal mesoporous silica structures (SBA-15) with uniform pore sizes up to approximately 300 angstroms. The SBA-15 materials are synthesized in acidic media to produce highly ordered, two-dimensional hexagonal (space group p6mm) silica-block copolymer mesophases. Calcination at 500 degrees C gives porous structures with unusually large interlattice d spacings of 74.5 to 320 angstroms between the (100) planes, pore sizes from 46 to 300 angstroms, pore volume fractions up to 0.85, and silica wall thicknesses of 31 to 64 angstroms. SBA-15 can be readily prepared over a wide range of uniform pore sizes and pore wall thicknesses at low temperature (35 degrees to 80 degrees C), using a variety of poly(alkylene oxide) triblock copolymers and by the addition of cosolvent organic molecules. The block copolymer species can be recovered for reuse by solvent extraction with ethanol or removed by heating at 140 degrees C for 3 hours, in both cases, yielding a product that is thermally stable in boiling water.