Structure analysis of montmorillonite intercalated with cetylpyridinium and cetyltrimethylammonium: Molecular simulations and XRD analysis

Molecular mechanics and molecular dynamics simulations combined with X-ray powder diffraction were used in structure investigation of montmorillonite intercalated with cetylpyridinium (CP) and cethyltrimethylammonium (CTA) ca tions. Molecular modeling revealed the interlayer structure and differences in intercalation behavior of CP and CTA cations in montmorillonite. The ex perimental and calculated values of basal spacing were in good agreement fo r both intercalates: in the case of CP-montmorillonite d(exp) = 20.59 Angst rom, d(calc)=20.60 Angstrom; for CTA-montmorillonite d(exp)=18.00 Angstrom and d(calc)=18.10 Angstrom. CTA-montmorillonite exhibits significantly high er total sublimation energy and higher host-guest interaction energy than t he CP-montmorillonite. The main difference between both intercalates is in charge distribution on the host layers and guest species. The charge transf er from the guest species to the host layer is higher in CTA-montmorillonit e than in CP-montmorillonite, and consequently the charge polarization betw een the host and guest layers is much higher in CTA-montmorillonite. This l eads to much stronger host-guest electrostatic interaction in the case of C TA-montmorillonite. (C) zool Academic Press.