摘要
为了研究三嵌段共聚物的自组装过程和SBA-15的形成机理,采用介观动力学(MesoDyn)方法模拟介孔分子筛SBA-15形成过程中模板剂P123与硅源试剂TEOS的协同自组装过程,并通过向体系引入稳恒剪切力来代替实际外力模拟了SBA-15六角介观相的形成过程,直观地展现了P123/硅酸物种超分子聚集体在SBA-15结构形成过程中的作用。模拟结果表明,P123与TEOS在水溶液中通过协同作用能够自组装形成尺寸均一的球状超分子聚集体,这是硅基有序介孔分子筛SBA-15形成过程中的前驱体:疏水的PPO嵌段团缩在该超分子聚集体的内部,在SBA-15分子筛形成中起决定性的致孔作用;亲水的PEO嵌段与包裹在胶束外部的TEOS相互交织在一起,其使得SBA-15在制备后期脱除模板剂后形成一些与主介孔相互连接的无规则微孔。在引入剪切力作用后,该P123/TEOS超分子聚集体不再自组装形成球状胶束,而是被拉扯成圆柱状的胶束,并且最终排列成为具有规则的六角形状的聚集结构,这一六角介观相则是介孔分子筛SBA-15的结构基础。今采用模拟条件,用水热法合成了高质量的SBA-15分子筛,通过XRD和高分辨透射电镜分析表明,模拟SBA-15形成过程的结果与实验合成的SBA-15具有相互吻合的完美二维六方结构。
In order to study the self-assembly process and understand the formation mechanism of the mesoporous silica SBA-15, the mesoscale dynamics simulation method （MesoDyn） was adopted to investigate the super-molecular assemble process between template （triblock copolymer P123） and silica source （TEOS） during the formation of SBA-15. The hexagonal mesophase formation process of SBA-15 was also studied by introducing a steady shear instead of the stirring in the actual experiments. Moreover, the effects of super-molecular aggregates （P123/TEOS） on the mesoporous silica SBA-15 formation process were analyzed too. The simulation results show that the uniform spherical super-molecular micelles can be assembled by template （triblock copolymer P123） cooperating with silica source （TEOS）, which are the precursors of SBA-15in the formation process. The hydrophobic PPO micelle cores play a decisive role in the uniform mesopores formation process of SBA-15, while the hydrophilic PEO micelle coronas insert into the silica matrix and form the micropores in SBA-15 after calcination. Since the steady shear is introduced into the simulation, the P123/TEOS super-molecular aggregates no longer form spherical micelles, but turn to form cylindrical micelles with hexagonal array which is the final structure form of SBA-15. In order to verify the simulation results, high quality SBA-15 was synthesized via hydrothermal method under the same conditions used in the simulation. The XRD analysis and TEM images clearly indicate that the experimentally synthesized SBA-15 has perfect 2D hexagonal structure which is in accordance with what the simulation indicated.
出处
《高校化学工程学报》
EI
CAS
CSCD
北大核心
2010年第3期422-428,共7页
Journal of Chemical Engineering of Chinese Universities
基金
国家自然科学基金(20536020
20876061)
教育部留学回国人员科研启动基金
863计划(2006AA06A310)
