This thesis is divided in two parts, as it deals with two main research areas. The first part describes experiments that examine the role of the morphology on the mechanical properties of polymer composite films, whereas the second part deals with the controlled self-assembly of polymer-tethered gold nanorods. For the first part of this thesis, core-shell latex particles were synthesized comprising high-glass transition temperature cores and low-glass transition temperature shells. From the latex particles, two types of composite films were prepared. One type of films featured a regular distribution of hard inclusions in a soft, elastomeric matrix, whereas the other type of film featured a more random distribution of the hard inclusions in the matrix. The mechanical properties of the two types of film were measured and compared at various test rates and temperature. The influence of the film morphology was extracted. At room temperature, the films with a random distribution of the hard particles showed higher hardness and stiffness than the films with an ordered distribution of the particles. At high temperature, the mechanical properties of the two types of film were comparable. In the second part of the thesis, gold nanorods were functionalized through the selective attachment of either polystyrene or polyN-isopropyl acrylamide) chains to their short facets. The polystyrene-modified gold nanorods were self-assembled into various structures in ternary mixtures of DMF/THF/water, by changing the ratio of the solvents in the mixtures. The polyN-isopropyl acrylamide)-modified gold nanorods were reversibly self-assembled into chains in water, by increasing the temperature of their water solution to above 33&degï¼›C. To our knowledge this is the first example of temperature-driven self-assembly of inorganic nanorods.