Hybrid technology for the preparation of PMMA/Laponite® nanocomposites

Abstract

Homogeneous poly(methyl methacrylate) nanocomposites were produced with a hybrid technology from Laponite® grafted with PMMA. The reinforcement was prepared by attaching PMMA chains to the surface of the silicate in in situ intercalative polymerization, then it was homogenized with PMMA in an internal mixer. Composites were prepared containing reinforcements with different lengths of the attached polymer chains. The structure of the composites was studied by scanning and transmission electron microscopy and X-ray diffraction, while their properties by DSC and tensile testing. Complete exfoliation was not achieved; the composites contained several individual silicate layers but mostly particles and/or tactoids of less than 200 nm size independently of the length of the attached polymer chains. The tactoids retained their ordered structure, although the arrangement of the layers was not very regular. The reinforcing effect of the grafted silicate was moderate and the properties of the composites were not as good as expected. However, larger molecular weight of the attached PMMA chains resulted in larger reinforcement and better properties. The strong interaction of the grafted chains and the silicate surface hindered the formation of entanglements between chains attached to the surface and the matrix polymer, and limited stress transfer as well. Other ways must be found in order to exploit the potentials of layered silicate nanocomposites as structural materials.