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Template synthesis of novel block copolymer ordered mesoporous carbon molecular sieve

Author: HuangZuo
Tutor: ZhaoDongYuan
School: Fudan University
Course: Inorganic Chemistry
Keywords: Triblock copolymers Mesoscopic structures Mesoporous materials Ordered Mesoporous Carbon material Fudan University Carbon precursor PhD thesis Surfactants Self-assembly method
CLC: TQ424.25
Type: PhD thesis
Year: 2008
Downloads: 2043
Quote: 2
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Abstract


As one of the most promising materials, ordered mesoporous carbons possess both remarkable functional properties and excellent chemical/thermal stability, which make them suitable for the applications in catalysts, sensors, bioreactors, energy storage and so on. Templating from proper block copolymers can lead to highly ordered mesostructure, which brings a series of opportunities in the development of creating various mesostructured carbonaceous frameworks. While this is a newly developed field, and there are still a lot of challenges in the synthesis of mesoporous carbon.This thesis focuses on the synthesis of mesoporous carbon from direct triblock copolymer templating approach. The present work is an attempt to synthesize mesoporous carbon with novel structure and explore new synthesis pathways.In chapter 2, mesoporous polymer and carbon with 2-D hexagonal （FDU-15） and body-centered cubic （FDU-16） structures were synthesized by employing F127 (PEO106-PPO70-PEO106) as templates, phenolic resol as precursor via evaporation induced self-assembly process. The influence factors on the mesostructure of FDU-15 and FDU-16, such as the choose of precursors and EISA process, were systematically studied by employing small angle X-ray scattering technique. The results can help to further understanding the formation mechanism of mesostructures from the organic-organic self-assembly system.In chapter 3, a synthesis of diamond-like face-centered 3-D cubic （Fd（?）m） mesostructure with open polymer and carbon frameworks was carried out by employing reverse triblock copolymer R1 PO50EO136PO50 as a template via EISA method. Structural model based on SAXS patterns and TEM images shows that the ordered mesostructure consists of 8 large and 16 small caged pores, of which 8 large cages are arranged tetrahedrally on a diamond-like lattice. Obvious bimodal pore size distribution at mean values of 3.2-4.0 and 5.4-6.9 nm with a small window size was observed in N2 sorption isotherms. Such mesostructure shows excellent thermal stability even to 1000℃. Bimodal caged size can a slightly adjusted by varying calcination temperature. The formation of the mesostructure may be related to the characteristic phase behaviors of reverse triblock copolymer PPO-PEO-PPO with long PEO chain. PPO-PEO-PPO/resol ratio is a key factor for the synthesis. Using PPO-PEO-PPO copolymers as templates has been proven to be an effective way to fabricate other new mesostructures that were thought only occurs in inversed lyotropic phase.In chapter 4, highly ordered mesoporous carbonaceous frameworks with variable cubic Fd（?）m, Im（?）m, Ia（?）d and hexagonal symmetries were successfully synthesized by using blend amphiphilic surfactants of reverse triblock copolymer R1 and F127 as the template and phenolic resol as carbon precursors via EISA strategy. The carbonaceous mesostructures can transform from high to low curvatures （Fd（?）m→Im（?）m→p6mm→Ia（?）d） by simply adjusting the ratio of R1: F127 and the ratio of copolymer: resol precursor. The PEO-PPO-PEO type and PPO-PEO-PPO type triblock copolymer can interplay and simultaneously contribute the micellization process and organic-organic self-assembly via hydrogen interaction to form intercrossing micelle networks.In chapter 5, highly ordered mesoporous polymer and carbon materials with variable symmetries were synthesized from the blends of HMTA treated novolac precursors and A-B-A type amphiphilic triblock copolymers via EISA strategy. The self-assembly force come from the intermolecular hydrogen bonding between hydrophilic PEO blocks and novolac matrix. Methylene released by HMTA at elevated temperature would lead to the crosslinking of novolac to from a thermosetting polymer. Compared to those prepared from resol prepolymer, the obtained mesoporous carbons also have uniformed mesopores, large surface areas and pore volumes. The synthesis strategy offers the potential to control not only the mesostructures, but also the composition of mesoporous polymer by using different curing agentsIn chapter 6, a simple one-step hydrothermal method was proposed for the synthesis of carbonaceous monoliths with hierarchical porosities by employing F127-P123 mixed triblock copolymer as templates and phenolic resol as a carbon precursor at 100℃. The monoliths show ordered 2-D hexagonal mesostructure with uniform pore size （- 3 nm） and 3-D irregular macroporous scaffolds with the size of around 3μm. The micro spherical and body-centered cubic mesoporous carbons with irregular shapes can also be obtained by only employing F127 as a template. This approach allows one-pot formation of both ordered mesostructure and irregular 3-D scaffolds, which will be considerably important for the facile production of hierarchical porous carbon materials.

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CLC: > Industrial Technology > Chemical Industry > Reagents and the production of pure chemicals > Adsorbent > Inorganic adsorbent > Used as artificial silicate adsorbent
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