层状双氢氧化物和蒙脱石的剥离及其自组装

以钙基蒙脱石为原料,氟化钠为钠化剂,十六烷基三甲基溴化铵为有机改性剂采用离子交换法制备了有机蒙脱石(CTA-MMT);以硝酸镁、硝酸铝、氢氧化钠和十二烷基磺酸钠为原料,采用水热法制备了有机型镁铝层状双氢氧化物(Mg Al-SDS-LDH);以氯仿为剥离介质,采用超声法剥离CTA-MMT和MgAl-SDS-LDH,分别获得了两种剥离型矿物溶胶,将其混合自组装制备了蒙脱石/层状双氢氧化物(MMT/LDH)组装材料。用XRD和AFM表征了CTA-MMT和MgAl-SDS-LDH及其剥离产物,并分析了组装材料的热稳定性。结果表明,CTA-MMT和MgAl-SDS-LDH在氯仿介质中剥离仅需20 min,剥离型CTA-MMT和MgAl-SDS-LDH片层平均厚度分别约为9和8 nm。MMT/LDH由剥离型CTA-MMT和MgAl-SDS-LDH片层有序组装而成,组装材料结构与MgAl-SDS-LDH和CTA-MMT的含量有关,其结构单元层间距2.59 nm(CTA-MMT含量较低时)随着组装材料中CTA-MMT含量的升高而转变为1.82 nm。MMT/LDH组装材料具有较单一的CTA-MMT或MgAl-SDS-LDH更高的热稳定性。

Exfoliation of layered double hydroxide and montmorillonite and their self-assembly

Organic montmorillonite (CTA-MMT) was prepared with the method of ion exchange by using calcium-montmorillonite as raw material, sodium fluoride as sodium agent and cetyl trimethyl ammonium bromide (CTAB) as organic modifier. Organic layered double hydroxide (MgAl-SDS-LDH) was synthesized by hydrothermal method by using the raw materials of magnesium nitrate, aluminum nitrate, sodium hydroxide and sodium dodecyl sulfonate (SDS). Sols of exfoliated MgAl-SDS-LDH and exfoliated CTA-MMT were obtained by exfoliation of MgAl-SDS-LDH and CTA-MMT in chloroform through ultrasonication. By mixing the two sols, montmorillonite/layered double hydroxide nanocomposite (MMT/LDH) was prepared by self-assembly of exfoliated products. The structures of MgAl-SDS-LDH, CTA-MMT and their exfoliated products were characterized by XRD and AFM. The thermal stability of MMT/LDH was characterized by thermogravimetric analysis. The results show that MgAl-SDS-LDH and CTA-MMT can be exfoliated in chloroform in merely 20 min. The average thicknesses of exfoliated CTA-MMT and exfoliated MgAl-SDS-LDH are 9 and 8 nm, respectively. MMT/LDH is a self-assembling material which is assembled orderly by exfoliated CTA-MMT and exfoliated MgAl-SDS-LDH, and the structure of MMT/LDH is influenced by the content of exfoliated MgAl-SDS-LDH and exfoliated CTA-MMT. The interlayer spacing of MMT/LDH decreases with the increase of content of exfoliated CTA-MMT, from 2.59 nm (in the case of low content of CTA-MMT) to 1.82 nm (in the case of high content of CTA-MMT). Furthermore, the thermostability of MMT/LDH is better than that of pristine MgAl-SDS-LDH or CTA-MMT.