【作者】 徐璐；

【导师】 李宝会；

【作者基本信息】 南开大学 ， 凝聚态物理， 2010， 博士

【摘要】 本论文主要应用量子化学理论计算结合固体核磁共振(NMR)实验技术,研究了系列结晶和非晶高分子体系的微观结构、氢键相互作用以及高分子共混物中的链段动力学行为。主要包括以下四方面研究内容：(一)研究两种结晶性高分子——等规和间规立构聚丙烯(iPP/sPP)中13C各向同性和各向异性化学位移。通过分析不同的初始构型构象、不同的优化方式对量化计算结果的影响,获得了正确计算结晶性高分子NMR化学位移的有效方法；同时讨论了采用γ-旁式效应解释不同立构聚丙烯的13C化学位移起源的成功和不足之处；研究了近年来发展的检测13C化学位移各向异性的两个重要NMR实验技术(SUPER和RAI)的优缺点和实验参数优化问题,测定了iPP样品的CSA粉末谱线形并与量化计算的理论预测结果相比较,显示理论与实验的很好符合。(二)采用量化计算结合固体NMR实验详细研究了三种不同立构聚乙烯醇(PVA)中复杂的氢键相互作用及其对13C化学位移的影响,阐明了长期存在争论的PVA中次甲基碳三重劈裂峰的微观起源,探索了与水形成分子间氢键对PVA化学位移的影响。量化计算结果可以很好地预言iPVA的NMR实验谱图；sPVA因为量化计算模型为高度间规,而实验样品是轻度间规而使理论和NMR实验结果间略有差别；对于aPVA建立了大量不同构型构象的局域链段模型展开系统研究,部分地阐明了其三重劈裂峰的起源。结果表明,研究PVA次甲基碳的三重劈裂峰的起源不应只考虑分子内氢键还应考虑分子间氢键的影响,只有一些特定构型构象下才能形成分子内氢键。从系列量化计算结果中我们总结出PVA中次甲基碳化学位移分布的规律如下：(1)包含单一氢键情形下,PVA中与次甲基相连的羟基充当质子受体时,次甲基碳的谱峰向低场偏移；充当质子给体时,次甲基碳的谱峰向高场偏移；(2)PVA同时参与一个分子内氢键与一个分子间氢键,次甲基碳的谱峰向低场偏移；(3)PVA间形成多重分子间氢键时次甲基碳的谱峰向高场偏移,与水形成多重分子间氢键时次甲基碳的谱峰向低场偏移。变温13C CP/MAS和SUPER等固体NMR实验进一步验证了量化计算结果的合理性。(三)基于国际上最近发展的用于质子间同核去耦的连续相调制多脉冲技术,我们发展了DF-CRAMPS和DQ-CRAMPS两种质子高分辨固态NMR新技术,分别用于获取有机固体中柔性和刚性质子信号进行选择性检测。这些技术应用于研究聚丙烯酸(PAA)体系中各种复杂的氢键结构,获得了高分辨的实验谱图并结合量化计算对不同氢键结构的化学位移进行了正确归属,首次在PAA中发现了几种新颖的氢键结构。(四)聚对乙烯基苯酚/聚氧乙烯(PVPh/PEO)共混物体系中氢键相互作用与链段动力学行为研究。通过高分辨二维1H-1H自旋交换和13C-1H分离局域场的固体NMR技术揭示了PVPh/PEO共混物中PVPh的酚羟基与PEO间的氢键相互作用以及不同组分的分子运动特性,发现了相容性共混物中链间弱相互作用导致的链间协同运动。更多还原

【Abstract】 In this thesis, combined quantum chemical calculation and solid-state NMR techniques were used to study the microstructure and hydrogen bond interaction in a series of crystalline and amorphous polymers, as well as segmental dynamics in polymer blends. This thesis basically consists of the following four parts:1. Studies on the chemical shifts of two types of crystalline polymers, isotactic and syndiotactic polypropylene (iPP/sPP). By analyzing the influence of different initial configurations, conformations and optimizing methods to quantum chemical calculation results, we obtained an effective method to accurately calculate NMR chemical shift in crystalline polymer. We also discussed the successes and shortcomings in elucidating the 13C chemical shifts of PP with different tacticities usingγ-gauche effect. We studied the merits and drawbacks, as well as the optimization of experimental parameters of two newly developed NMR techniques (SUPER and RAI) for recoupling the chemical shift anisotropy. The CSA powder lineshapes of iPP were successfully obtained, which were also compared with quantum chemical calculation results. It was found that the results of quantum chemical calculation are in good accordance with NMR experimental results.2. Combined quantum chemical calculations and solid-state NMR experiments were used to investigate the complex hydrogen bonds and their influence to 13C chemical shifts in three types of polyvinyl alcohol (PVA) with different tacticities. We have succecesfully elucidated the nature of methine triplets of 13C NMR spectrum in PVA and explored the influence of the intermolecular hydrogen bonds between PVA and water on the chemical shifts. Quantum chemical calculation is able to predict the 13C NMR spectrum of iPVA well. For sPVA, because the used structural model was highly syndiotactic while the experimental sample is slightly syndiotactic, thus the theoretical prediction was a little different with the NMR result. Plenty of structural models with different configurations and conformations were built for aPVA, and quantum chemical calculation partly clarified the origin of the methine triplets. Our results show that we should not only take into account intramolecular but also intermolecular hydrogen bonds when studing the origin of the triplets, and intramolecular hydrogen bond can be only formed at certain particular configurations and conformations. Through a series of quantum chemical calculation results, some basic rules of chemical shift distribution of methine carbons in PVA were summarized: (1) In case of only one hydrogen bond, when the hydroxyl group in PVA is proton acceptor, the peak of methine carbons moves toward low field, and when the hydroxyl group in PVA is proton acceptor, the peak of methine carbons moves towards high field; 2) when the hydroxyl group in PVA is involved in an intramolecular hydrogen bond and an intermolecular hydrogen bond, the peak of methine carbons moves towards low field; (3) when multiple intermolecular hydrogen bonds is formed between different PVA chains, the peak of methine carbons moves towards high field, and when multiple intermolecular hydrogen bonds is formed between PVA and water, the peak of methine carbons moves towards low field. Variable-temperature 13C CP/MAS and SUPER solid-state NMR experimental results further confirmed the conclusion obtained from quantum chemical calculation.3. On the basis of recently developed continuous phase modulation techniques for homonuclear decoupling among protons, we proposed two new high resolution solid-state 1H NMR techniques:DF-CRAMPS and DQ-CRAMPS, which are used to obtain mobile and rigid proton signals in organic solids. These techniques were then used to study various types of complex hydrogen bond structures in polyacrylic acid (PAA). We have obtained high resolution’H NMR spectra and correctly assigned the NMR peaks associated with hydrogen bonds according to experimental and quantum chemical calculation results. Several new hydrogen bond structures were found for the first time in PAA.4. Studies on the hydrogen bonds and segmental motion in poly-4-vinylphenol/polyethylene oxide (PVPh/PEO) blends. Through high resolution 2D solid-stae NMR techniques including 2D 1H-1H spin exchange experiment and 13C-1H separated-local-field NMR experiment, we revealed the hydrogen bond interaction between the phenolic hydroxyl in PVPh and PEO as well as molecular mobility of different components in PVPh/PEO blends; we also found an interchain cooperation motion in compatible blends resulting from interchain weak interaction.更多还原