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

Fuyou Ke; Jinhui Yi; Shu Zhang; Shuiqin Zhou; Peter I Ravikovitch; Michal Kruk

doi:10.1016/j.jcis.2019.02.057

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

J Colloid Interface Sci. 2019 May 15:544:312-320. doi: 10.1016/j.jcis.2019.02.057. Epub 2019 Feb 19.

Authors

Fuyou Ke¹, Jinhui Yi², Shu Zhang², Shuiqin Zhou², Peter I Ravikovitch³, Michal Kruk⁴

Affiliations

¹ Department of Chemistry, College of Staten Island, City University of New York, 2800 Victory Boulevard, Staten Island, NY 10314, USA.
² Department of Chemistry, College of Staten Island, City University of New York, 2800 Victory Boulevard, Staten Island, NY 10314, USA; Ph.D. Program in Chemistry, The Graduate Center of the City University of New York, 365 Fifth Avenue, New York, NY 10016, USA.
³ ExxonMobil Research and Engineering Company, 1545 Rt 22 East, Annandale, NJ 08801, USA.
⁴ Department of Chemistry, College of Staten Island, City University of New York, 2800 Victory Boulevard, Staten Island, NY 10314, USA; Ph.D. Program in Chemistry, The Graduate Center of the City University of New York, 365 Fifth Avenue, New York, NY 10016, USA. Electronic address: Michal.Kruk@csi.cuny.edu.

PMID: 30861436
DOI: 10.1016/j.jcis.2019.02.057

Abstract

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.

Keywords: Hollow nanosphere; Mesoporous nanotube; Micelle templating; SBA-15; Swollen micelle.