十二烷基硫酸钠在水滑石层间的插层行为研究

The conformation of sodium dodecylsulfate pillars in layered double hydroxides

采用13C和27Al固体核磁共振表征方法结合XRD及热分析等表征技术,对十二烷基硫酸钠(NaDS)柱撑的水滑石(Mg2Al-NO3-)的分子结构进行了研究。结果表明,柱撑物中的有机相存在两种不同的构形,外表面吸附的DS-主要是以活动性较好的无序构形状态存在,进入层间的DS-主要是以活动性差的有序构形状态存在。NaDS柱撑LDHs中有序构形的量随DS-溶液浓度的增加而增加,当溶液中DS-的物质的量达到水滑石阴离子交换容量(AEC)的2倍或更大时,层间DS-的量保持为57%左右。NaDS柱撑水滑石的铝核周围的配位为单一的六配位环境,此环境在柱撑前后没有发生明显变化。

13C CP/MAS NMR, 13C MAS NMR and 27Al MAS NMR measurements have been used in a study of sodium dodecylsulfate pillared layered double hydroxides （LDHs） of the type Mg2Al-NO3^- ）assisted by XRD and TG-DTA, etc. It was found that the surfactant co-exists in two forms in the pillared materials, a relatively mo-bile disordered phase adsorbed on the surface of the material and an ordered relatively immobile phase intercalated in the interlayer galleries, with the proportion of the latter increasing with increasing dodecylsulfate anion （DS^-） concentration. The anions were found to be intercalated in the interlayer galleries in a monolayer with a perpendicular orientation of the chains with respect to the layers. The amount of intercalated DS^- with ordered conformation in the LDHs was found to increase with increasing concentration of DS^- in the solution, until it reached a level of double the anionic exchange capacity of the LDH. It was suggested that every aluminum ion in the material is coordinated to 6 ligands and that their chemical environment is not noticeably changed after the intercalation process.