Physical Review Materials, 2018, vol 2, 12, pp. 123605
DOI:10.1103/PhysRevMaterials.2.123605
Abstract
Metal-polymer nanocomposites are hybrid materials combining the superior plasmonic, electrical, and thermal properties of metals with the good elasticity and manufacturability of polymers. This renders metal-polymer nanocomposites promising candidates for conductive filler and coating applications, where mechanical properties are optothermally coupled. Here, we study the interplay of nanostructure, thermoplasmonics, and elastic mechanical properties of silver-polystyrene nanocomposites (AgPS) by transmission electron microscopy, small-angle x-ray scattering, Brillouin light scattering (BLS), and other supplemental techniques. We utilize the well-known particle-brush architecture to ensure a homogeneous and isotropic nanoparticle distribution throughout the hybrid material. The effective longitudinal modulus of the as-prepared samples is found to decrease from 5.7 to 4.8 GPa with increasing Ag content from 0 to 4.4 vol.%. Temperature-dependent BLS measurements reveal the unique contribution of local thermoplasmonic heating that depends on the Ag nanoparticle composition. This thermoplasmonic effect results in a lower apparent glass transition temperature (Tg) and a stronger laser power dependence of the speed of sound. Exceeding moderate thermal annealing temperatures (>150∘C) leads to a strong structural rearrangement within the homogeneous nanocomposite material with a peculiar clustering-redispersion effect, which also translates into altered mechanical properties. The annealing-induced Ag nanoparticle aggregation results in an even stronger thermoplasmonic effect. We validate our experimental findings with complementary thermographic measurements and finite-element modeling. Overall, this work demonstrates the combined effects of composition and (reversible) aggregation on the mechanical and thermoplasmonic properties of metal-polymer nanocomposites. It not only deepens our understanding of the interaction between light, temperature, and mechanical properties in metal-polymer nanocomposites but also provides a guide for customizing AgPS nanocomposites for potential applications.
