www.springerlink.com/content/e810u86w2783537q/

Temperature dependent synthesis of micro- and meso-porous silica employing the thermo-responsive homopolymer poly(N-isopropylacrylamide) or the random copolymer poly(N-isopropylacrylamide-co-acrylic acid) as structure-directing agent (SDA) and Na2SiO3 as silica source is proposed. The thermo-responsive character of the SDA provides the advantages including (1) temperature dependent synthesis of microporous silica, hierarchically micro-mesoporous silica, and mesoporous silica just by changing the aging temperature below or above the low critical solution temperature of the thermo-responsive SDA, and (2) elimination of the thermo-responsive SDA from silica matrix by water extraction. The synthesis mechanism is discussed, and the effect of the aging temperature and the weight radio of SDA/Na2SiO3 on the synthesis of micro- and meso-porous silica are studied. Microporous silica, hierarchically micro-mesoporous silica and mesoporous silica with the surface area at 3.5-9.0 x 10(2) m(2)/g and the pore volume at 0.28-1.13 cm(3)/g and the average pore size ranging from 1.1 to 9.0 nm are synthesized. The strategy affords a new and environmentally benign way to fabricate porous silica materials, and is believed to bridge the gap between the synthesis of microporous and mesoporous silica materials.