One of the storage conditions affecting quality of food stuffs due to short shelf life is temperature. Thermal insulation can be achieved by adding phase change materials (PCMs) to packaging materials. PCMs store and release latent heat of phase change during melting and crystallization operations, respectively. Thus, they can provide thermal protection for packaged foods. The aim of this study is to prepare new food packaging materials poly (ethylene terephthalate)-poly (ethylene glycol) (PET-PEG) multiblock copolymers as solid-solid phase change materials (SSPCM) as potential food packaging materials with thermal energy storage (TES) property. Polyesterification was carried out with PEG at different average molecular weights (1000, 4000 and 10,000 g/mol), ethylene glycol (EG) and terephthaloyl chloride (TPC). Synthesized PET-PEG multiblock copolymers were characterized using Fourier transform infrared (FT-IR) spectroscopy and differential scanning calorimetry (DSC) methods. The crystal structures of PET-PEG multiblock copolymers were characterized by polarized optical microscopy (POM) and their surface properties were determined by performing contact angle tests. TES capacity of the PET-PEG multiblock copolymers was found in range of 26.1-150.5 J/g. Consequently, this study demonstrates the potential of PET-PEG multiblock copolymers suitable for effective thermal preservation in packaging material applications to maintain the quality of packaged food stuffs.