Kaolinite–poly(methacrylamide) intercalated nanocomposite via in situ polymerization

Abstract

The preparation and characterization of a kaolinite–methacrylamide intercalation compound was achieved by a guest-displacement method, the direct treatment of a dimethylsulfoxide (DMSO) pre-intercalate with an aqueous solution of methacrylamide under mild conditions, giving intercalation ratios up to 92% and an expansion of 0.53 nm of the interlayer space. The DMSO molecules were fully displaced from the interlayer space by methacrylamide. Only partial intercalation could be obtained with N-methylformamide (NMF) pre-intercalate. After intercalation, the monomer was thermally polymerized at 100 or 150 °C with various heating times. XRD, FTIR, 13C CP/MAS NMR, and thermogravimetric analysis confirmed that polymerization was partially achieved in the interlayer spaces, while the layered structure of kaolinite was maintained, constraining the polymer in an interlayer space of 0.57 nm in the c-direction. In good agreement with the TG data, elemental analysis gave a stoichiometry of Al2Si2O5(OH)4·(C4H7NO)0.52 for the thermally treated methacrylamide intercalate, corresponding to a ratio of one methacrylamide unit per two kaolinite structural units. The thermal stability of the methacrylamide intercalate was increased after thermal treatment and polymerization.Key words: kaolinite, intercalation, nanocomposites, aluminosilicates, layered materials, interlayer polymerization, poly(methacrylamide).