A polymer thin film includes polyethylene having a molecular weight of at least approximately 250,000 g/mol, and has an elastic modulus of at least approximately 25 GPa, a tensile strength of at least approximately 0.8 GPa, and a thermal conductivity of at least approximately 5 W/mK. Formation of the polymer thin film may include forming a polymer solution from a crystallizable polyethylene and a liquid solvent, forming a gel from the polymer solution, forming a polymer thin film from the gel by calendering or solid state extrusion, and stretching the polymer thin film.