Properties and Characterization of Organoclay/Dimethacrylate Composites Obtained by In Situ Photopolymerization

Summary: Composites of dimethacrylates/organoclay were obtained by in situ photopolymerization of Bis-GMA (Bisphenol A glycidyl methacrylate) and TEGDMA (tetraethyleneglycol dimethacrylate) in the presence of camphorquinone and DEEMA (2-(diethylamino)ethyl methacrylate). The composites contained up to 10% wt/wt of organoclays. Monomer conversion and polymerization kinetics were determined by real time Fourier-Transform Infrared Spectroscopy – Attenuated Total Reflectance (FTIR-ATR), and showed an increase of conversion with addition of the clay. The storage modulus E' of the composites also had a marked dependence on the composite composition and increased with addition of clay at all temperatures. T_g also increases with clay content. X-Ray Diffraction (XRD) analysis shows that the clay is completely exfoliated for the composites with a lower proportion of clay, whereas for larger clay/polymer proportions peaks corresponding to the interlamellar distance of the clay are still observed. This is probably due to the fact that the amount of monomers in the initial formulation was not sufficient to delaminate the clay. Scanning Electron Microscopy (SEM) images indicate a quite homogenous copolymer, with some clay aggregates that increase in size and number for the higher filler loadings in agreement with the XRD results.