Influence of solvent washing on interlayer structure of alkylammonium montmorillonites

Powdered samples of montmorillonite were functionalized with alkylammonium ions of various chain lengths and subjected to two different constant volume washing procedures: water only or sequential ethanol–water. The alkylammonium montmorillonites were analyzed with X-ray diffraction and differential scanning calorimetry to obtain insights into the effect of washing procedure. The ethanol–water procedure greatly reduced the amount of surfactant present that was not bound by cation exchange, and in some instances affected the crystallinity of the surfactant. Additionally, contact angle measurements on the compacted alkylammonium montmorillonites were obtained to assess the effect of functionalization and washing on the wettability of two common epoxides used in clay–epoxy nanocomposites. Regardless of surfactant treatment, the alkylammonium montmorillonites with ethanol–water washing exhibited lower contact angles for the epoxides, which is consistent with lower final surfactant content.

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► Contact angle of epoxides on alkylammonium montmorillonite was affected by washing.
► Solvent choice altered interlayer surfactant conformation and concentration.
► Clay minerals with mixed surfactants resulted in poorly ordered interlayer structure.