Modification of mechanical properties in polymer nanocomposites by the incorporation of specific self-complementary hydrogen bonding interactions

The dispersion, aggregate morphology, and interfacial strength of fillers in polymer nanocomposites are crucial in determining their physical properties. Here, we utilize the quadruple hydrogen bonding group ureidopyrimidinone (UPy) to investigate enthalpic effects on the dispersion of silica nanoparticles in a poly(butyl acrylate) copolymer matrix and to correlate dispersion with mechanical properties. Butyl acrylate was copolymerized with an UPy side chain functional methacrylate monomer and blended with silica nanoparticles containing various degrees of UPy, hexyl, or silanol surface functionality. The tensile and dynamic mechanical responses of these nanocomposites were measured, and the effects of varying surface functionality on mechanical properties are discussed and correlated to dispersion by TEM. The competing effects of filler-filler, matrix-filler, and matrix-matrix hydrogen bonding lead to a system where both the type and amount of filler surface functionality are of critical importance to the material's final strength.