Abstract
Understanding the interlayer swelling and molecular packing in organoclays is important to the formation and design of polymer nanocomposites. This paper presents recent experimental and molecular simulation studies on a variety of organoclays that show a linear relationship between the increase of
d-spacing and the mass ratio between organic and clay. A denser molecular packing is observed in organoclays containing surfactants with hydroxyl–ethyl units. Moreover, our simulation results show that the head (nitrogen) groups are essentially tethered to the clay surface while the long hydrocarbon chains tend to adopt a layering structure with disordered conformation, which contrasts with the previous assumptions of either the chains lying parallel to the clay surface or being tilted at rather precise angles.
Molecular simulations show that the alkyl chains of organoclay surfactants pack in a disordered conformation but with a tendency for layering. The measured and calculated gallery spacings increase in proportion to the mass of the surfactant consistent with a given mass density of the confined organic material with good agreement between experiment and simulation.