Study on preparation and mechanism of organic montmorillonite with different functional groups

The influence of functional groups on the organic intercalation of montmorillonite (Mt) was discussed in this article by intercalating Mt with four organic compounds containing different cationic functional groups. The maximum intercalation amounts of hexadecyl trimethyl ammonium bromide (CTAB), benzylcetyldimethyl ammonium chloride (HDBAC), bromohexadecyl pyridine (HIB), and 1-hexadecyl-3-methylimidazolium chloride (HMC) were 0.96, 0.81, 0.73, and 0.61 mmol/g, respectively. Molecular simulations revealed that the functional groups influenced the arrangement status of organic cations in the Mt interlayers. It found out that the minimum distances between the nitrogen atom in CTAB, HDBAC, HIB, and HMC and the surface oxygen of Mt were 2.939 ± 0.05, 2.554 ± 0.11, 3.703 ± 0.07, and 3.360 ± 0.08 Å, respectively. Molecular size was also shown to influence intercalation since CTAB was more easily intercalated than the larger HDBAC. Moreover, the benzene ring in HDBAC weakened the interaction between its chains, which decreased its intercalation amount. The –N+ functional groups of HIB and HMC were located on the benzene ring, which weakened their cationic exchange ability. In summary, the functional groups affected the intercalation amount, intercalation rate, and their arrangement (parallel or vertical) in Mt. These results were used to explore the intercalation mechanism of Mt, which can be used to guide the production of novel organic Mt compounds.