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首页> 外文期刊>Advanced Functional Materials >Lamellar Mesostructured Silicas with Chemically Significant Hierarchical Morphologies
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Lamellar Mesostructured Silicas with Chemically Significant Hierarchical Morphologies

机译：具有重要化学分层形态的层状介孔结构二氧化硅

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摘要

We describe the hierarchical structures of mesostructured silicas assembled from electrically neutral and unsymmetrical Gemini surfactants of the type C_nH_(2n+1)NH(CH_2)_mNH_2 with n = 10, 12, 14 and m = 3, 4. As expected for Gemini surfactants with an all anti-chain configuration and a packing parameter near 1.0, lamellar framework structures are formed, regardless of the length of the alkyl chain (n) and the number of carbon atoms (m) linking the two amino group centers. However, different layer curvatures and levels of hierarchical structure are observed depending on the delicate balance between the hydrophilic interactions at the surfactant head group-silica interface and the hydrophobic interactions between the surfactant alkyl groups. For Gemini derivatives with n = 12 or 14 and m = 3 or 4, well-expressed hierarchical vesicles are formed that are analogous to those assembled previously from Gemini surfactants with m = 2. However, for n = 10, a new coiled slab structure (m = 3) and an onion-like core-shell structure (m = 4) are formed. In addition, a previously unobserved stripe-like silica structure is obtained from a C~0_(12+2+0) Gemini surfactant in combination with an α,ω-diamine co-surfactant. The relative stability of these hierarchical structures depends on the delicate competition between the long-range elastic forces occurring in the hydrophobic region of the assembled surfactant and the short-range chemical forces in the hydrophilic moiety. Lamellar silicas with hierarchical vesicular structures, the new coiled slab, and stripe-like phases promise to be chemically significant morphologies, because they can minimize the framework pore length and provide optimal access to the framework walls under diffusion-limited conditions.
机译：我们描述了由电中性和不对称的C_nH_（2n + 1）NH（CH_2）_mNH_​​2类型的电中性和非对称Gemini表面活性剂组装而成的介孔结构二氧化硅的层级结构，n = 10、12、14和m = 3、4。具有所有的反链构型和接近1.0的堆积参数，无论烷基链的长度（n）和连接两个氨基中心的碳原子数（m）如何，都形成了层状骨架结构。然而，根据在表面活性剂头基-二氧化硅界面处的亲水相互作用与表面活性剂烷基之间的疏水相互作用之间的精细平衡，观察到不同的层曲率和层次结构水平。对于n = 12或14且m = 3或4的Gemini衍生物，会形成表达良好的分层囊泡，类似于先前由m = 2的Gemini表面活性剂组装而成的囊泡。但是，对于n = 10，则为新的卷曲平板结构（m ＝ 3）和洋葱状的核-壳结构（m ＝ 4）形成。另外，从C〜0_（12 + 2 + 0）双子表面活性剂与α，ω-二胺助表面活性剂组合获得先前未观察到的条纹状二氧化硅结构。这些分层结构的相对稳定性取决于在组装的表面活性剂的疏水区域中发生的远距离弹性力与在亲水性部分中的近距离化学力之间的微妙竞争。具有层状囊状结构，新的螺旋状平板状和条状相的层状二氧化硅有望成为化学上重要的形态，因为它们可以使骨架孔长度最小化，并在扩散受限的条件下提供进入骨架壁的最佳通道。

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