Encapsulation of Anionic Dye Molecules by a Swelling Fluoromica through Intercalation of Cationic Polyelectrolytes

To develop a novel layered host material with the ability to encapsulate anionic substances, the intercalation of three cationic polyelectrolytes into synthetic sodium fluortetrasilisic mica (Na-TSM) was investigated. With polyethylenimine (PEI) and poly(allylamine hydrochloride) (PAH), the conformation of the intercalated polycation and its ability to accommodate anionic guests depended on its state of protonation. The quaternary ammonium polycation poly(diallyldimethylammonium) (PDDA), which had the lowest charge density of the three polymers studied, adopted a coiled conformation within the anionic host at both high and low pH, resulting in an excess of cationic sites within the interlayer of the polysilicate. Powder X-ray diffraction patterns and adsorption isotherms showed two different stages of PDDA intercalation with different adsorption free energies. Atomic force microscopy images showed that the PDDA−clay nanocomposites maintained the shape of the original nanosheets, indicating the successful conversion of the lamellar host into a 2D material with anion exchange capacity. The anion-accepting ability of these nanocomposites was quantified by studying the encapsulation of a bulky anionic blue dye as a function of the loading of PDDA. From dehydration and X-ray powder diffraction experiments, it was concluded that the dye−polyelectrolyte−clay nanocomposites possessed two kinds of interlayer galleries, and the anionic dye was site-selectively intercalated into hydrated galleries in which PDDA strands were coiled.