Next-level improvements in thermal extremity protection for the current Extended Cold Weather Clothing System (ECWCS) are needed for soldiers in order to improve mobility and achieve peak performance in bitterly cold Arctic climes. In this STTR program, 2W iTech LLC proposes to develop phase change material (PCM) based thermal regulating films, in collaboration with the Multiscale Thermal Science team at the University of Massachusetts Lowell (UMass Lowell). The proposed film can be directly integrated into the textile layers of the ECWCS for thermal comfort management. Compared to state-of-the-art PCM-containing textiles, the proposed thermal regulating film will possess high thermal regulating performance, high breathability, wide applicability, high scalability, high durability, and low fabrication cost. The proposed efforts will leverage 2W iTechs related experience developing porous membranes. Thermal transport simulation of a PCM-film-laminated garment will be performed by the UMass Lowell Team to guide the development of the proposed PCM composite films. The feasibility of the proposed approach will be demonstrated in Phase I. Three material samples will be delivered at the end of Phase I. Technologies at the end of Phase I will be at TRL 4.