Effect of Layer Charge on the Formation of Polymer/Layered Silicate Nanocomposites: Intercalation of Polystyrene

Reduced-charge montmorillonites (RCMs), layered silicates of variable charge density, were modified with alkylammonium (AA) cations to prepare organophilic materials with variable surface activities. The intercalation of polystyrene (PS) from melts was investigated by X-ray diffraction. Slight differences in layer charge density significantly affected the activity of organoclays. The specimens based on high charge RCMs, which had been premodified with long-chain AA cations, exhibited the highest activities to intercalate PS. Expansion of some organically modified silicates based on small AA cations in PS melts led to higher d 001 values. On the other hand, the presence of the largest AA cations significantly reduced free space for polymer intercalation. This study may help with designing strategies for choosing appropriate inorganic fillers for polymer nanocomposites to control their structure and properties. Understanding of the layer charge effect can help to explain some controversial results in the literature, when seemingly similar materials of organoclays exhibited different properties and interactions with polymers.