Synthetic High-Charge Organomica: Effect of the Layer Charge and Alkyl Chain Length on the Structure of the Adsorbed Surfactants

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• 作者：M. Carolina Pazos ; Miguel A. Castro ; M. Mar Orta ; Esperanza Pav贸n ; Jes煤s S. Valencia Rios ; Mar铆a D. Alba
• 刊名：Langmuir
• 出版年：2012
• 出版时间：May 15, 2012
• 年：2012
• 卷：28
• 期：19
• 页码：7325-7332
• 全文大小：320K
• 年卷期：v.28,no.19(May 15, 2012)
• ISSN：1520-5827

文摘

A family of organomicas was synthesized using synthetic swelling micas with high layer charge (Na_nSi_8-nAl_nMg₆F₄O₂₀路XH₂O, where n = 2, 3, and 4) exchanged with dodecylammonium and octadecylammonium cations. The molecular arrangement of the surfactant was elucidated on the basis on XRD patterns and DTA. The ordering conformation of the surfactant molecules into the interlayer space of micas was investigated by ¹³C, ²⁷Al, and ²⁹Si MAS NMR. The arrangement of alkylammonium ions in these high-charge synthetic micas depends on the combined effects of the layer charge of the mica and the chain length of the cation. In the organomicas with dodecylammonium, a transition from a parallel layer to a bilayer-paraffin arrangement is observed when the layer charge of the mica increases. However, when octadecylammonium is the interlayer cation, the molecular arrangement of the surfactant was found to follow the bilayer-paraffin model for all values of layer charge. The amount of ordered conformation all-trans is directly proportional of layer charge.