Tuning the Mechanical Properties of Poly(Methyl Acrylate) via Surface-Functionalized Montmorillonite Nanosheets

Polymer layered silicate nanocomposites (PLSNs) made of montmorillonite (MMT) nanosheets and poly(methyl acrylate) (PMA) are synthesized and systematically characterized. MMT is first modified with a surface-bound monomer and then functionalized with PMA via radical addition-fragmentation chain transfer (RAFT) polymerization using a grafting through approach. PMA-modified MMT nanosheets with grafted polymer chains of variable length are obtained. The successful surface modification is demonstrated by near-field scanning optical microscopy, thermogravimetric analysis, attenuated total reflection Fourier transform infrared spectroscopy, small-angle X-ray scattering, and size-exclusion chromatography. The mechanical properties of various nanocomposites are evaluated via tensile testing. It can be shown that the mechanical properties (Young's modulus, tensile strength, toughness, and ductility) of these PLSNs can be fully controlled by using two major strategies, i.e., by the variation of the overall content of polymer-modified MMT and by the variation of the chain length of the surface-grafted polymer.