Enhancing the Mechanical Properties of Matrix-Free Poly(Methyl Acrylate)-Grafted Montmorillonite Nanosheets by Introducing Star Polymers and Hydrogen Bonding Moieties

Abstract

Matrix-free nanocomposite films of poly(methyl acrylate) (PMA) and montmorillonite (MMT) nanosheets that imitate the microscopic structure of nacre are developed and their mechanical properties are studied in detail via tensile testing. The exfoliated MMT nanosheets are grafted with PMA via a grafting-through radical addition–fragmentation chain transfer polymerization in presence of a surface-anchored ionic monomer. The mechanical properties are precisely tailored a) via the variation of the degree of polymerization of the surface-grafted polymer, illustrating the impact of chain entanglement and the MMT content on the performance of the material, and b) via cross-linking of the surface-grafted polymer, either by partial change of the polymer topology from linear to star-shape or by the introduction of hydrogen-bonding units within the polymer. These experiments demonstrate the strong influence of the chain mobility of the surface-grafted polymer on the mechanical properties of the nanocomposite material.