Intercalation via ion-dipole bonding

There is a host of other organic molecules that possess both a hydrophilic and hydrophobic portion in the molecule. This is exactly the criteria needed to form an ion-dipole bond to the cation with the hydrophilic end of the molecule forcing the hydrophobic portion away from the surface. A classic example of this can be seen with alkyl pyrrolidones. 

Intercalates form readily between the n-alkyl pyrrolidones and yield interesting effects as a function of alkyl length and ratio of pyrrolidone to surface cation [6]. When utilizing n-dodecyl pyrrohdone (DDP) as a surface treatment, it was found that when DDP was mixed with the clay in a 1 1 ratio to the exchangeable cation, there was an interdigitated intercalate with a r/-spacing of 2.1 nm, which is quite similar to that observed for traditional quaternary amine treated clays. 

This can be observed in an increase of the d-spacing to 3.5 nm. The self-assembly was observed in alkyl chains as small as eight carbons and strongly reinforced by longer chain lengths of Cl8. 

Another variation of the ion-dipole surface treatment method utilizing bloek copolymers has been reported [8]. In this approach, one of the blocks of the copolymer can readily ion-dipole bond to the cations on the clay surface and the other block is compatible with the polymer of interest. Polyethylene oxide is very effective as the block that bonds to the clay surface cations and lies nearly parallel to the clay surface, and the other block is tailored to the polymer of interest and forms loops extending away from the clay surface, better to interact with the polymer. 

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