Evolution of Solution Structures during the Formation of the Cubic Mesoporous Material, KIT-6, Determined by Double Electron-Electron Resonance
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- 作者：Sharon Ruthstein ; Daniella Goldfarb
- 刊名：Journal of Physical Chemistry C
- 出版年：2008
- 出版时间：May 8, 2008
- 年：2008
- 卷：112
- 期：18
- 页码：7102 - 7109
- 全文大小：256K
- 年卷期：v.112,no.18(May 8, 2008)
- ISSN：1932-7455
文摘
Double electron-electron resonance (DEER) is employed to explore the evolution of solution structures duringthe formation of the bicontinuous cubic (Ia
d) mesoporous material KIT-6. We focused on the early stagesof the reaction, where micellar structures are not well-resolved in the micrographs of cryogenic transmissionelectron microscopy (cryo-TEM). KIT-6 is synthesized with Pluronic P123 block copolymers, PEO20PPO70PEO20, as a template. Initially, the aqueous solution, held at 40 
C, consists of Pluronic P123 micelles, whichare characterized by a hydrophilic corona, comprising the poly(ethylene oxide) (PEO) blocks, and a hydrophobiccore, consisting of the poly(propylene oxide) (PPO) block. The variations in the volume of the hydrophobiccore of the micelles as a consequence of the addition of the silica source (TEOS, tetraethoxyorthosilane)were evaluated using a hydrophobic spin-probe, 4-hydroxy-tempobenzoate (4HTB), which is localized in thehydrophobic core of the micelles. The measurements were carried out on solutions that were freeze-quenchedat different times after the addition of TEOS (tetraethoxyorthosilane). New details on the formation of KIT-6were obtained, revealing swelling of the hydrophobic core during the first ~10 min of the reaction followedby a contraction, close to the original size. The swelling was attributed to penetration of the TEOS and itshydrolysis products into the micelles.
d) mesoporous material KIT-6. We focused on the early stagesof the reaction, where micellar structures are not well-resolved in the micrographs of cryogenic transmissionelectron microscopy (cryo-TEM). KIT-6 is synthesized with Pluronic P123 block copolymers, PEO20PPO70PEO20, as a template. Initially, the aqueous solution, held at 40 C, consists of Pluronic P123 micelles, whichare characterized by a hydrophilic corona, comprising the poly(ethylene oxide) (PEO) blocks, and a hydrophobiccore, consisting of the poly(propylene oxide) (PPO) block. The variations in the volume of the hydrophobiccore of the micelles as a consequence of the addition of the silica source (TEOS, tetraethoxyorthosilane)were evaluated using a hydrophobic spin-probe, 4-hydroxy-tempobenzoate (4HTB), which is localized in thehydrophobic core of the micelles. The measurements were carried out on solutions that were freeze-quenchedat different times after the addition of TEOS (tetraethoxyorthosilane). New details on the formation of KIT-6were obtained, revealing swelling of the hydrophobic core during the first ~10 min of the reaction followedby a contraction, close to the original size. The swelling was attributed to penetration of the TEOS and itshydrolysis products into the micelles.