NON-TECHNICAL SUMMARY: Two-thirds of polymers are semicrystalline, and these are among the most widely and extensively used materials in our lives. Controlling the crystalline and amorphous structures that make up all semicrystalline polymers remains a fundamental issue for developing and optimizing their properties and applications. It is therefore important to understand the crystalline and amorphous structures of semicrystalline polymers. Most previous work focused on analysis of the crystalline structures. In this project, the PI aims at understanding the amorphous structure and the crystalline-amorphous interface of semicrystalline polymers. Using advanced spectroscopic techniques to understand interfacial and amorphous structures together with their crystalline counterparts, and studying dynamical processes, the project is focused on elucidating the crystallization and molecular re-organization pathways of semicrystalline polymers. A successful project will contribute to controlling the structures and properties of semicrystalline polymers and developing novel energy-efficient processing approaches. TECHNICAL SUMMARY The crystallization pathways of semicrystalline polymers have been debated for many decades, partly as a result of lack of understanding of the amorphous structure in the initial state as well as during the crystallization process. In this project, the PI and his team aim at elucidating the amorphous structure of semicrystalline polymers, making