This project aims to shed light on a centrally important but controversial issue in polymer crystallization, namely the trajectory of the molecular chains throughout the crystal and to answer the question of how do polymer chains deposit at the growth front in polymer crystals. The PI proposes a new experimental scheme to elucidate the chain trajectory of polymers in bulk and single crystals based on 13C selective isotope labeling and advanced solid-state NMR. Here, combined use of 1) specific isotope labeling, 2) 13C-13C spatial correlation, and high resolution NMR will allow to access chain trajectory (adjacent re-entry fractions and directions) of polymer chains in the crystalline regions. Using this new strategy, the PI will investigate how i) chemical structures such as functions, chemical defect, and molecular weights, ii) kinetics, and iii) entanglements influence chain trajectory in crystalline regions. This information is particularly important for understanding polymer crystallization on a molecular level.
Polymers are important synthetic materials whose properties depend critically on the structure of their constituent crystals. While their structures have been studied for decades, details of the location and trajectory of individual polymer molecules (which resemble very long chains) are still uncertain. Techniques used so far have led to disagreements and controversial interpretations in the literature. The PI proposes a combination of new advanced magnetic resonance methodologies and precise chemical labeling of the polymer molecules to help shed an answer to these questions. The students will benefit from interdisciplinary education in polymer chemistry and physics, as well as gaining expertise in advanced characterization techniques.