Transition from transparent aerogels to hierarchically porous monoliths in polymethylsilsesquioxane sol-gel system
Transition from transparent aerogels to hierarchically porous monoliths in polymethylsilsesquioxane sol-gel system
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DOI：
10.1016/j.jcis.2011.02.027
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发表时间：
2011-05-15
影响因子：
9.9
通讯作者：
Hanada, Teiichi
中科院分区：
文献类型：
--
作者：
Kanamori, Kazuyoshi;Kodera, Yasunori;Hanada, Teiichi
用含表面活性剂Pluronic F127的溶胶-凝胶体系研究了聚甲基倍半硅氧烷(PMSQ)CH3SiO1.5凝胶从大孔和中孔的分级孔结构到均匀中孔的转变。甲基三甲氧基硅烷(MTMS)的前驱体经历了酸/碱两步反应，其中水解和缩聚分别在酸性和碱性水介质中进行，为一锅反应。通过改变F127的浓度来控制多孔的形态。足够浓度的F127抑制了疏水性PMSQ凝析油的微米级相分离(调幅分解)，并由于胶体网络在大量溶剂中的形成而得到了定义良好的具有高比孔容的介孔透明气凝胶。相分离通过降低F127的浓度在微米范围内调节清晰的大孔。在相分离形成的富含PMSQ的凝胶结构域中，PMSQ胶体网络形成中孔，形成具有分级大孔和中孔结构的整体式PMSQ凝胶。由于PMSQ中甲基的柔性网络和相互排斥作用，这些凝胶中的中孔在蒸发干燥时不会坍塌。(C)2011 Elsevier Inc.保留所有权利。
A transition from hierarchical pore structures (macro- and meso-pores) to uniform mesopores in monolithic polymethylsilsesquioxane (PMSQ CH3SiO1.5) gels has been investigated using a sol-gel system containing surfactant Pluronic F127. The precursor methyltrimethoxysilane (MTMS) undergoes an acid/base two-step reaction, in which hydrolysis and polycondensation proceed in acidic and basic aqueous media, respectively, as a one-pot reaction. Porous morphology is controlled by changing the concentration of F127. Sufficient concentrations of F127 inhibit the occurrence of micrometer-scale phase separation (spinodal decomposition) of hydrophobic PMSQ condensates and lead to well-defined mesoporous transparent aerogels with high specific pore volume as a result of the colloidal network formation in a large amount of solvent. Phase separation regulates well-defined macropores in the micrometer range on decreasing concentrations of F127. In the PMSQ-rich gelling domain formed by phase separation, the PMSQ colloidal network formation forms mesopores, leading to monolithic PMSQ gels with hierarchical macro- and meso-pore structures. Mesopores in these gels do not collapse on evaporative drying owing to the flexible networks and repulsive interactions of methyl groups in PMSQ. (C) 2011 Elsevier Inc. All rights reserved.