Poly(methyl methacrylate)-kaolinite nanocomposites prepared by interfacial polymerization with redox initiator system

Abstract

Interfacial intercalative polymerization of methyl methacrylate (MMA) was developed to prepare PMMA-kaolinite nanocomposites using a redox initiator system, based on dodecylamine as reductant, immobilized into kaolinite by successive intercalation while the oxidant component of the redox system (K₂S₂O₈) was applied from aqueous phase. The X-ray diffraction (XRD) was used to prove the functionalization of the clay with the amine before starting the polymerization reaction. The progress of the polymerization reaction through the involvement of the amine in the initiation process was confirmed not only by successfully performing the reaction at 50 °C, a temperature at which the K₂S₂O₈ cannot start the polymerization alone, but also by the enhancement of polymerization rate and drop in activation energy required to start the polymerization. The produced PMMA/kaolinite nanocomposites were examined by XRD and transmission electron microscope as well; both confirmed the defoliation of the kaolinite layers into homogeneously distributed platelets within the polymer phase which supports the effectiveness of the redox initiation in the intercalative polymerization. Furthermore, more explanation about the interfacial structure of the nanocomposites was given using Fourier transform infrared. The thermal gravimetric analysis revealed a very similar behavior above 300 °C with respect to the pure PMMA prepared under the same reaction conditions while in the range from 220 °C to 320 °C, the degradation was earlier in the case of the nanocomposites due to the presence of the dodecylamine; on the other hand, the glass transition temperatures were increased remarkably as assigned by differential scanning calorimetry in comparison with the pure PMMA.