HDTMA^+柱撑蒙脱石的^(13)C MAS NMR谱研究

^(13)C MAS NMR Study of HDTMA^+ Pillared Montmorillonite

采用13C魔角旋转核磁共振技术(MASNMR),对HDTMA+柱撑蒙脱石层间域内由于堆垛密度差异所致的具不同排列方式的有机离子的构形进行了研究。结果表明,长链烷基在层间并不是完全刚性的(All trans)状态,同时由不同构形离子组成的有机相之间的比例也不是不变的,而是随着有机离子在层间域内堆垛密度的增大,柱撑离子存在着一个从类似固体状态(Solid like)到类似液体状态(Liquid like)再到类似固体状态变化的宽范围的分子环境。其中平卧双层排列模式中有机分子所表现出的类似液体的性质最为明显,只有在较高堆垛密度的倾斜双层排列模式下层间离子才表现出较明显的类似固体状态。

The conformations of the surfactant (HDTMA+) in the intercalated montmorillonite have been investigated using solidstate13C MAS NMR spectroscopy. The NMR spectra clearly demonstrate that the coexistence of Alltrans and Gaucheconformations. As the result of increasing the packing density of HDTMA+ in the interlayer of montmorillonite, the relative contents of the phases formed by different conformations varied from solidlike state to liquidlike state, then to solidlike state. In the lateralbilayer model, the chains of the surfactants are disordered similar to that in a liquidlike crystalline state whereas those are ordered similar to that in a solidlike crystalline state in the paraffintypebilayer model.