title: Intercalation of dodecylamine into kaolinite and its layering structure investigated by molecular dynamics simulation.
abstract: Dodecylamine was successfully intercalated into the layer space of kaolinite by utilizing the methanol treated kaolinite-dimethyl sulfoxide (DMSO) intercalation complex as an intermediate. The basal spacing of kaolinite, measured by X-ray diffraction (XRD), increased from 0.72 nm to 4.29 nm after the intercalation of dodecylamine. Also, the significant variation observed in the Fourier Transform Infrared Spectroscopy (FTIR) spectra of kaolinite when intercalated with dodecylamine verified the feasibility of intercalation of dodecylamine into kaolinite. Isothermal-isobaric (NPT) molecular dynamics simulation with the use of Dreiding force field was performed to probe into the layering behavior and structure of nanoconfined dodecylamine in the kaolinite gallery. The concentration profiles of the nitrogen atom, methyl group and methylene group of intercalated dodecylamine molecules in the direction perpendicular to the kaolinite basal surface indicated that the alkyl chains within the interlayer space of kaolinite exhibited an obvious layering structure. However, the unified bilayer, pseudo-trilayer, or paraffin-type arrangements of alkyl chains deduced based on their chain length combined with the measured basal spacing of organoclays were not found in this study. The alkyl chains aggregated to a mixture of ordered paraffin-type-like structure and disordered gauche conformation in the middle interlayer space of kaolinite, and some alkyl chains arranged in two bilayer structures, in which one was close to the silica tetrahedron surface, and the other was close to the alumina octahedron surface with their alkyl chains parallel to the kaolinite basal surface.
authors: School of Geoscience and Surveying Engineering, China University of Mining & Technology, Beijing 100083, China.
authors: Shuai
authors: S
authors: Zhang
authors: School of Geoscience and Surveying Engineering, China University of Mining & Technology, Beijing 100083, China. Electronic address: lqf@cumtb.edu.cn.
authors: Qinfu
authors: Q
authors: Liu
authors: School of Geoscience and Surveying Engineering, China University of Mining & Technology, Beijing 100083, China.
authors: Hongfei
authors: H
authors: Cheng
authors: School of Geoscience and Surveying Engineering, China University of Mining & Technology, Beijing 100083, China.
authors: Xiaoguang
authors: X
authors: Li
authors: Department of Earth Science and Engineering, Taiyuan University of Technology, Taiyuan 030024, China.
authors: Fangui
authors: F
authors: Zeng
authors: School of Chemistry, Physics and Mechanical Engineering, Science and Engineering Faculty, Queensland University of Technology, 2 George Street, GPO Box 2434, Brisbane, Queensland 4001, Australia. Electronic address: r.frost@qut.edu.au.
authors: Ray L
authors: RL
authors: Frost
keywords: Dodecylamine; Intercalation; Kaolinite; Layering structure; Molecular dynamics simulation