多维核磁共振波谱方法研究含氟高分子结构

Fluoropolymers are important commercial materials ideally suited for protective coatings, lubricants and membrane barriers; in applications that expose them to extreme environments, require extreme longevity or require unusual surface properties. Detailed characterization of fluoropolymers is critical as there is a direct relationship between a polymer's structural features and its chemical, physical and mechanical properties. Correlation between polymer properties, synthesis conditions, and amount and type of structures permits polymer scientist to reproduce the preparation of material with optimum performance. Solution NMR produces sharp, accurate and sensitive signals. It is one of the most important methods to characterize polymers. In the past, because of the poor solubilities in most solvents, the characterization of fluoropolymers were often carried with analytical methods other than solution NMR, such as GPC, MS or IR, even solid state NMR etc. The results came from those resources could not provide abundant information for the fine structure analysis of fluoropolymers.The goal of this work is to provide examples of using Modern n-dimensional NMR and PANSY techniques to characterize a series of fluoropolymers including: Nafion, Tedlar, Krytox and Viton. Simple and clear peak patterns will be acquired within short time period by using the special designed modern n-dimensional NMR with PANSY techniques. Fine structures of fluoropolymers will be studied and related reactions mechanism will be understood. Standard procedures for studying fluoropolymers' structures by NMR will be developed. The results will help with the improvements of current fluoropolymers industry and also promote a better usage of the NMR instruments.

含氟高分子工业应用广泛，是耐腐蚀涂料，耐高/低温润滑剂和膜交换材料等领域的理想材料。为达到通过控制反应条件提高其性能的目的，需要对其化学结构与性能和合成反应条件的关系进行研究。液体核磁共振波谱信号准确，灵敏，是表征化合物的有力手段。过去，由于含氟高分子溶解性问题，其结构测定通常使用其他分析手段，结果无法满足对其精细结构研究的需要。本项目选择合适溶剂对一系列含氟材料进行液体核磁共振波谱研究。其中包括：Nafion 离聚物，Tedlar PVF 聚氟乙烯，Krytox 全氟聚醚和Viton 含氟橡胶。通过多维核磁方法对选定区域选择性激发和去耦，可以在短时间内得到信号清晰，峰型简单的谱图。便于确定化学结构，了解反应机理。更结合平行检测核磁手段(PANSY)节约采集时间，提高检测效率，增加信噪比。可建立起快速高效液体核磁检测含氟高分子材料的标准流程。推动我国含氟材料结构测定水平的提高。

本项目通过平行采集核磁 (PANSY)，扩散序谱(DOSY)等新型核磁方法结合多维核磁对一系列含氟材料包括：聚偏氟乙烯PVF，全氟聚醚PFPE及聚偏氟乙烯-二氟丙烯酸共聚物PVDF-co-DFAA等含氟橡胶进行液体核磁共振波谱研究。PANSY方法节约采集时间，提高检测效率，增加信噪比。19F DOSY区别于传统1H DOSY，加入adiabatic形状脉冲，在19F谱较大谱窗内均匀激发信号；优化梯度时间，消除19F-19F同核耦合造成的19F谱信号畸变。利用DOSY检测含氟聚合物的扩散速率，对区分链端与主链结构，聚合物长链端基与支化短链端基扩散行为的区别及含量分析，分子量和分子量分布测定有重要意义。本项研究对同样有较宽谱窗，较大同核J耦合常数的元素如31P和195Pt的DOSY研究也具有重大意义。