Chain Trajectory of Semicrystalline Polymers in Bulk and Single Crystals by Solid-state NMR

技术摘要：本项目旨在阐明聚合物结晶中一个重要但有争议的问题，即分子链在整个晶体中的轨迹，并回答聚合物链如何在聚合物晶体的生长前沿存款的问题。 PI提出了一种新的实验方案，以阐明基于13 C选择性同位素标记和先进的固态NMR的块状和单晶聚合物的链轨迹。在此，1）特定同位素标记、2）13C-13C空间相关性和高分辨率NMR的组合使用将允许访问结晶区域中聚合物链的链轨迹（相邻的再进入分数和方向）。使用这种新策略，PI将研究i）化学结构（如功能，化学缺陷和分子量），ii）动力学和iii）缠结如何影响结晶区域中的链轨迹。 这些信息对于在分子水平上理解聚合物结晶特别重要。非技术性概述：聚合物是重要的合成材料，其性能关键取决于其组成晶体的结构。 虽然它们的结构已经研究了几十年，但单个聚合物分子（类似于非常长的链）的位置和轨迹的细节仍然不确定。 到目前为止所使用的技术导致了文献中的分歧和有争议的解释。 PI提出了一种新的先进的磁共振方法和聚合物分子的精确化学标记的组合，以帮助回答这些问题。 学生将受益于聚合物化学和物理学的跨学科教育，并获得先进表征技术的专业知识。

TECHNICAL SUMMARY: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.NON-TECHNICAL SUMMARY: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.