Reversible Diels-Alder chemistry was exploited to develop thermo-responsive polymer films. Here, low molecular weight poly(styrene) (PS) and poly(ethylene glycol) (PEG) were prepared with furyl and maleimido chain ends, respectively. These polymers were then tethered together to form a thiol-terminated PEG-b-PS diblock copolymer ligand via a Diels-Alder linkage and were employed to randomly disperse 10 nm diameter Au nanoparticles within a matrix of PEG. Thermal treatment caused the Diels-Alder linkages between the polymer blocks to be severed, resulting in controllable surface functionalization due to phase separation. Migration of the Au nanoparticles to the surface of the films was characterized by Rutherford backscattering spectroscopy, small-angle X-ray scattering, contact angle measurements, and atomic force microscopy.