Modification of Montmorillonite and Prediction of Polymer/Clay Affinity Using Surface Properties and Lattice Model

Sodium montmorillonite (Na-MMT) was organically modified using 11- aminoundecanoic acid (AUA) and methacryloxyethyltrimethylammonium chloride (MAETAC) via cation exchange reaction. The effect of the modifier type and concentration on the structure and surface properties of the organically modified montmorillonites (OMMTs) was investigated. According to the results, the basal spacing of organoclays was enlarged considerably with increasing the AUA concentration, while increasing the MAETAC concentration had no significant influence on OMMT’s gallery height. On the other hand, contact angle measurements revealed that increasing the modifiers concentration would increase the hydrophobicity of pristine montmorillonite. The FTIR spectra showed that the OMMTs interlayer environment changed from liquid-like to solid-like as the modifier concentration increased. A mean-field lattice-based model was applied to various polymer/OMMT systems to predict the affinity between the prepared OMMTs and some polymers with different hydrophobicity. The model results showed that high polar and hydrophilic polymers, such as poly(ethylene oxide), exhibit more negative free energy change and stronger interaction with the OMMTs and, consequently, higher potential for preparation of composites with desirable nanostructure and mechanical properties.