AEC Tri-Block Anionic Surfactant Templating Mothod For Synthesizing Thick-Wall Mesoporous Materials

The highly ordered mesoporous materials have attracted much attention in chemistry and material communities since the first synthesis of M41S via a structure directing agent (SDA) method in the early 1990s. Because of the large surface area, large pore volume, tunable pore size within 2~50 nm, highly ordered and various mesostructure, these mesoporous materials are expected to be applied in chemical industry, biomedicine, environmental protection and new energy sources. Recently, a great deal of work has been dedicated to the investigation of the mesostructure and pore properties of the mesoporous materials and many disadvantages have been discovered, such as low mechanical strength, low thermal and hydrothermal stability, which limited their application area in the industry. Therefore, synthesizing mesoporous materials with thick wall and controllable wall thickness should be deeply considered and solved first. In the regard to this, our work focused on synthesizing targeted mesoporous silicas with thick wall via a surfactant molecular design. By designing the structure of the surfactant molecules, we have obtained mesoporous silicas with a controllable wall thickness.In the first chapter, the background of the mesoporous materials were summarized, including formation mechanism, synthesis method, characterization, the control of the mesostructures, stability and potential applications.In the second charpter, a novel tri-block surfactant molecule fatty alcohol ether carboxylate (AEC: CnH2n+1-(EO)m-COONa) is selected and designed. Highly ordered 2D-hexagonal p6mm thick walled mesoporous silicas are synthesized by using this surfactant. Interestingly, it is found that the wall thickness of the mesoporous silica synthesized using AEC surfactant is much larger, reached ~3.4 nm. A rational scheme is mentioned to describe the assembly process that the existence of two different types of hydrophilic head groups leads to the formation of double-layer silica framework, resulting to an increase in the wall thickness. The subsequent synthesis of carbon inverse replicas using AEC surfactant templated mesoporous silicas as hard templates, demonstrates our strategy of using two types of head groups in series to initiate double-layer silica condensation. According to the mechanism, the wall thickness of the AEC surfactant templated mesoporous silicas can be well controlled by chaging the EO length of the surfactant molecules. Moreover, it is also investigated that the hydrothermal stability of mesoporous silicas synthesized with different templates, finding that AEC surfactant templatied mesoporous silicas perform a highly hydrothermal stability, resulting from the larger wall thickness. The quaternary ammonium or amino group functionalized thick wall-mesoporous silica after extraction will exhibit more potential applications in scientific areas.In the third chapter, the formation of the mesophases in the C12H25O(CH2CH2O)10CH2COOH/TMAPS/NaOH synthesis system of AEC surfactant templated mesoporous silica is discussed and full-scaled synthesis-field diagram is presented. Based on the mesophase diagram, the mesophase area for synthesizing 2D hexagonal p6mm thick walled mesoporous silicas is determined. It can be obviously observed that 2D hexagonal p6mm thick walled mesophase is formed in the synthesis system with low mole ratio of TMAPS (TMAPS/C12H25O (CH2CH2O)10CH2COOH = 0.43 ~ 1.0) and a mildly alkaline degree (NaOH/ CH2CH2O)10CH2COOH = 0.45 ~ 1.2).In the last chapter, we sum up the work and propose the outlook...