US EPA

5068503 

Journal Article 

Structures and dimensions of micelle-templated nanoporous silicas derived from swollen spherical micelles of temperature-dependent size 

Ke, F; Yi, J; Zhang, S; Zhou, S; Ravikovitch, PI; Kruk, M 

2019 

Yes 

Journal of Colloid and Interface Science
ISSN: 0021-9797
EISSN: 1095-7103 

544 

312-320 

English 

30861436 

10.1016/j.jcis.2019.02.057 

Subambient temperatures are employed in Pluronic-block-copolymer-templated syntheses of many large-pore silicas: SBA-15 (2-D hexagonal with cylindrical mesopores), FDU-12 (face-centered cubic with spherical mesopores), nanotubes and hollow nanospheres. Herein, the origin of a significant temperature dependence of the unit-cell parameter and pore diameter of silicas templated by swollen micelles of Pluronics under subambient conditions was elucidated. The temperature dependence of size of swollen spherical micelles of Pluronic F127 (EO106PO70EO106) in 2 M HCl solution was studied in 12-25 °C range using dynamic light scattering and was correlated with structure types, unit-cell sizes and pore sizes of silicas synthesized at four silica-precursor/Pluronic ratios with a swelling agent (toluene, ethylbenzene). The increase in size of swollen micelles with temperature decrease was paralleled by the increase in the unit-cell size and pore diameter, even if the micelle shape changed in the process of formation of the micelle-templated silica. The decrease in the silica-precursor/Pluronic F127 ratio at constant temperature triggered a succession of phases, including SBA-15 - nanotube sequence that may involve an intermediate nanotube bundle structure, which is uncommon and potentially useful. The temperature decrease also led to a succession of phases, including FDU-12 - SBA-15, hollow nanospheres - nanotube bundles, and nanotubes - SBA-15 sequences.