【作者】 沈怡；

【导师】 武培怡；

【作者基本信息】 复旦大学 ， 高分子化学与物理， 2006， 博士

【摘要】 本论文围绕二维相关光谱技术在聚合物研究中的应用展开。二维相关光谱技术的概念由Noda于1986年首先提出，并于1993年完善成广义二维相关光谱技术。由于其相对一维光谱来说，有较高的分辨率，同时能够辨明所研究的材料分子内各基团或分子间的相互关系，所以作为一维光谱的辅助分析手段，在很多研究领域得到了广泛应用。本文着重于采用二维相关光谱技术研究外扰引起的聚合物的结构和构象变化，从而得到材料结构和性能之间相互关联的信息。论文正文共分六个章节。第一章为全文的引言。第二章中我们研究了三种高分子材料：聚噻吩、聚氯噻吩、羰基铬配位的聚乙烯基咔唑。首先，我们运用二维拉曼光谱分别研究了聚噻吩和聚氯噻吩在降温和升温过程中的结构变化。研究发现掺杂聚噻吩中，中性态链段中的噻吩环以碳碳单键相连，所以有较大的自由度，容易发生构象的调整，对温度变化较为敏感。而氧化态链段中噻吩环以碳碳双键相连，体现为较为刚性的构象，所以对温度变化并不敏感。但掺杂后产生的分子链上的正电荷使得聚氯噻吩氧化态链段容易受到大气中水分和氧气的攻击，而加热过程无疑加剧了这一反应的进行，所以在我们观察的温度范围内(升温过程)，氧化态结构就已经逐渐在还原，链结构发生明显改变。在这个工作的基础上，我们进一步用二维红外光谱研究了羰基铬配位的聚乙烯基咔唑在升温过程中的结构变化。通过定量分析，我们发现这个聚合物材料的玻璃化转变温度为75-95℃，与文献中DSC数据相符。同时，我们还利用二维红外光谱的数据明确了羰基峰的归属。更为重要的是，我们发现这个材料在140℃以上，羰基铬基团会从配体上脱落下来，从而在一定程度上可能导致材料光电性能的下降。第三章中我们运用二维红外光谱着重从分子层面研究了甲壳型液晶高分子PMPCS的相变行为。首先我们通过定量分析确定了PMPCS的液晶相变温度区域为120-160℃。然后我们运用二维相关光谱来分析相变前后不同基团在热扰动下的运动变化顺序。我们发现升温过程中，主侧链尽管对温度有不同的响应，但是都调整构象进行取向，从而促使PMPCS的液晶相发育。在相变温度区域前，由于处于玻璃化温度下，分子链被“冻结”，所以整个分子链对热扰动都不敏感，但侧链因为相对来说有较大的自由度所以对热扰动稍有一定的响应。当温度升到相变区域时，分子链获得外界的能量，能够较为自由的调整构象。此时，柔顺的主链开始对热扰动变得异常敏感，而侧链上庞大且刚性的液晶基团在很大程度上限制了侧链的充分运动。所以从二维谱来看，主链对温度的响应速度快于侧链。总的来说，相变过程调整了主侧链之间的相互关系。另外，二维相关分析还区分出了处于无定型态和有序态下的基团特征峰，且证明了无定型态经历相变温度后逐渐演化成有序态，说明分子链构象逐步调整，最终形成液晶态。第四章中我们运用二维紫外光谱研究了逐层有序组装膜：(聚3-乙酸噻吩和聚4-乙烯基吡啶)_n(PTAA／P4VP)_n的成膜机理和膜瓦解过程中的组分结构变化。首先，我们以浓度为外扰对成膜过程中的紫外谱图进行了二维相关分析。研究发现PTAA比P4VP更容易组装，结合对成膜驱动力和组分分子结构的分析，我们推导出了(PTAA／P4VP)_n LBL膜的增长模型。我们认为P4VP柔性链的特质使其采取无规线团的构象缠绕在刚性PTAA链周围，由此缩短了相邻两层PTAA之间的距离，促使相邻两层PTAA分子链之间氢键的形成。在这种状态下，较为明确的层界限仅出现在不同的双层之间，而同一个双层内，PTAA单层和P4VP单层之间的界限非常模糊。其次，我们利用氢键的pH敏感特性分别用二维紫外光谱(以时间为外扰)考察了酸性和碱性水环境对膜结构的影响。在碱性水环境中，PTAA被离子化，PTAA与P4VP以及PTAA与PTAA之间的氢键均被破坏，膜结构迅速瓦解。而在酸性水环境中，P4VP的质子化只瓦解了PTAA与P4VP之间的氢键，而对PTAA之间的氢键没有造成特别大的影响，所以PTAA之间仍存在一定的层次结构，以致于膜的消除非常缓慢。总的来说，我们利用二维紫外相关分析得到的数据不仅建立了一个合理的PTAA／P4VP膜增长模型，还对膜在不同pH值水环境下组分的变化做了合理阐释，证实二维紫外相关分析在解释机理方面的可行性。第五章中我们运用二维衰减全反射红外光谱研究了水在聚合物膜中的动态吸附和扩散行为。我们研究了水在两种截然不同的聚合物材料：亲水性聚酰亚胺衍生物PISA和疏水性聚丙烯PP中的吸附扩散行为。均是采用二维相关光谱法分析一维ATR-FTIR动态谱图，得到关于水分子的不同状态和水分子的动态扩散行为的一些信息。首先均是利用二维相关光谱法高分辨率的优势研究羟基伸缩振动区域，从而划分出具有不同氢键强度的水分子状态。同时研究发现疏水性材料PP中，基本只存在水-水相互作用的水分子状态，而亲水性材料PISA较为复杂，除了水-水作用的水分子状态，还有水-聚合物不同基团相互作用下的水分子状态。其次，根据二维相关峰的正负信号来判别不同水分子状态在时间外扰下的变化顺序，以此来研究水分子的动态扩散行为。研究发现不同水簇状态(微观)的扩散速率主要受水簇体积大小的影响。而总体外扰水在材料中的吸附量和扩散系数(宏观)主要受聚合物材料的亲疏水性的影响。第六章是对全文所有体系的总结。对所有体系来说，我们的主要研究手段均为二维相关光谱。首先我们记录体系的动态光谱，然后利用二维相关光谱的优势分辨出若干小峰和弱峰，从而把体系中处于不同构象或不同相态的基团区分开来。然后再利用相关光谱可分辨光谱信号变化顺序的独特优点，找出各种状态下的基团在外扰影响下的相互关系，最终探寻相关的机理。另一方面，从上述介绍我们可以看出，我们把二维相关分析技术运用到了多种光谱中。红外光谱历来是二维相关分析法应用最为广泛的一种光谱技术，本文中也有所涉及。此外，在对导电高分子的研究中，我们把二维技术运用到了拉曼光谱中。更为重要的是，本文一个章节还尝试了二维分析方法在紫外光谱中的应用。就作者所知，二维紫外光谱在机理解释方面的应用实例非常少，而本文中的尝试不仅证实了二维紫外的可操作性，同时还拓展了二维紫外光谱技术的应用范围。更多还原

【Abstract】 This thesis centers on the application of two-dimensional （2D） correlation spectroscopy on the study of some representative polymeric systems. 2D correlation spectroscopy was proposed by Noda in 1986. And in 1993, it had been developed as "Generalized 2D Correlation Spectroscopy". Compared with conventional one-dimensional （ID） spectroscopy, 2D correlation spectroscopy owns the high resolution and it can distinguish the motion sequential order of the different functionalities of polymers. Thus, it is often looked upon as a useful initial probing tool to aid in the analysis of complex ID spectra and has received wide applications in the different fields. This thesis lays attention on the study of the perturbation-based structural/conformational changes of polymers by 2D correlation spectroscopy. The information can help us set up the relationships between the structure and property of polymers.The thesis contains six chapters. Chapter one is the introduction of the whole research work. In chapter two, three different polymers: polythiophene （PTh）, poly （3-chlorothiophene） （PCTh） and poly（N-vinylcarbazole） Cr（CO）₃ （PVKC） have been studied. Firstly, we have studied the thermal-based structural changes of PTh and PCTh using 2D Raman correlation spectroscopy. In doping PTh, the thiophene rings in the neutral species are connected by C-C bonds. Thus, it is easier for the neutral species to adjust the conformation under the thermal perturbation. On the other hand, the thiophene rings in the oxidized species are connected by C=C bonds. Lowering the temperature cannot easily change the conformation of the oxidized species. Thus, the oxidized species are not very sensitive to the temperature in the cooling process. However, in the heating process, the oxidized species are generally reduced to the neutral species. The occurrence of the structural change is due to that positively charged segments in PCTh are susceptible to a nucleophilic attack by oxygen or water and the increase of the temperature seems to accelerate the reaction processes, leading to the reduction of the oxidized species finally.On the basis of this work, we further investigate the thermal-based structural change of PVKC in the heating process using 2D FTIR correlation spectroscopy. The T_g of PVKC （75-95℃） is confirmed according to the result of the quantitative analysis, which is in accordance with the result of DSC experiment. A tentative assignment of carbonyl bands is also made using the information shown in the 2D spectra. More importantly, the detailed analysis show that the chromium tricarbonyl group may lose its bond with the aromatic ring in the ligand after 140°C, leading to the loss of the optical property.In chapter three, we have studied the mechanism of the liquid-crystalline （LC） phase development of a representative mesogen-jacketed liquid crystal polymer, poly{2,5-bis[（4-methoxyphenyl） oxycarbonyljstyrene} （PMPCS） using 2D FTIR correlation spectroscopy. The phase transition range 120°C-160°C is examined according to the result of the quantitative analysis. 2D correlation analysis is performed on the temperature-dependent IR spectra to probe the sequential order of changes in the different functionalities of PMPCS. The results show that both the backbone and side chain contribute to the LC phase development, although the functional group responsible for the formation of liquid-crystalline phase is located only in the side chain.Before the phase transition, the conformational change of individual side chains occurs sooner than that of the backbone due to the larger freedom of the side chains. After the phase transition, however, the readjustment of still somewhat mobile backbone occurs before the ordered, rigid, and mutually interacting side chains. That is, phase transition leading to the LC phase formation brings in a new cooperative restriction of motions to the segments. In addition, the earlier motion of the functionalities in disordered conformational state compared to those with ordered conformation under the thermal perturbation probably explains the relative ease of development of LC phase in PMPCS.In chapter four, the fabrication and denudation process of （poly（3-thiophene acetic acid） / poly（4-vinylpyridine））_n （（PTAA/ P4VP）_n） layer-by-layer （LBL） films has been studied by 2D UV-vis correlation spectroscopy. The UV-vis spectra are used to do the 2D correlation analysis. The results show that PTAA has a faster adsorption rate than P4VP. Combining the driving force of （PTAA/ P4VP）_n multilayers, we have proposed a model to describe the construction of the multilayer film. P4VP chaintakes advantage of its flexible property to entangle around the rigid backbone of PTAA, which largely shortens the distance between the neighboring PTAA chains. Thus, it is reasonably proposed that there exist hydrogen bonds between the neighboring PTAA chains. Accordingly, the borderline can only be distinguished between the bilayers and there is no clear borderline between PTAA and P4VP in each bilayer of the multilayer films.As we know, hydrogen bonds are sensitive to pH value. We have further investigated the influence of the acid and alkaline aqueous solutions to the structure of multilayers using 2D UV-vis spectroscopy. In the alkaline aqueous solution, PTAA is ionized and two different types of hydrogen bonds （I: hydrogen bonds between PTAA and P4VP chains; II: hydrogen bonds between PTAA and PTAA chains） are destroyed, leading to the rapid deconstruction of the multilayers. In the acidic aqueous solution, the protonation of P4VP only destroys the hydrogen bonds between PTAA and P4VP chains. On the other hand, the hydrogen bonds between PTAA and PTAA chains still exist because PTAA dissociates slightly at low pH value. Thus, the rate of the deconstruction in the acidic solutions is much slower compared with that in the alkaline solutions.In a word, the information shown in the 2D UV-vis spectra not only helps us set up a model of the construction process, but also provides a reasonable explanation of the change of the components in the deconstruction process. This work proves the feasibility of 2D UV-vis spectroscopic technique.In chapter five, we have studied the dynamic diffusion behavior of water in the polymeric membranes using 2D ATR-FTIR correlation spectroscopy. Two different polymeric materials: poly（4’4-oxydiphenylene pyromellitimide） （PMDA-ODA）/silica nanocomposite （PISA） and polypropylene （PP） have been studied. The dynamic ID ATR-FTIR spectra were firstly recorded and then we apply 2D correlation analysis to gain the information about the state of water molecules and the dynamic diffusion behavior.Firstly, we take advantage of the high resolution of 2D spectroscopy to separate the different states of water molecules according to the different strength of hydrogen bonds. In PP matrix, water molecules have no interaction with PP network because PP is a hydrophobic material. Thus, the hydrogen bonds only exist between the water molecules. However, in PISA matrix, water molecules have interaction with PISAnetwork because PISA is a hydrophilic material. Thus, the hydrogen bonds refer to several formations: H-bonding formed between the water molecules, H-bonding formed between water molecule and silicic acid （residues）, H-bonding formed between water molecule and PI system.Secondly, we distinguish the motion sequential order of the different states of water molecules according to the signals of 2D cross-peaks. The study shows that the volume of the water clusters influences the diffusion rate, while the property of the polymer influences the amounts and diffusion coefficient of the water molecules.Chapter six is the conclusion to the whole research work. The main technique used in all the work is the 2D correlation spectroscopy. Firstly, we record the dynamic spectra of the polymeric materials. Secondly, we take advantage of the high resolution of 2D spectroscopy to separate the weak bands and originally overlapped bands in the ID spectra. Accordingly, we can distinguish the groups in different states and conformations. Thirdly, 2D correlation analysis can often simplify spectral features corresponding to various inter- and intramolecular interactions, so we can elucidate the relationships between different groups and further search the related mechanism.On the other hand, in this thesis, we apply the 2D correlation analysis to different ID spectroscopies. The most useful research technique is the 2D FTIR correlation spectroscopy. And in this thesis, we have applied this method to the study of PVKC and PMPCS. Additionally, we have applied 2D Raman correlation spectroscopy to the study of conducting polymers. More importantly, we also tried the 2D UV-vis correlation spectroscopy in one chapter. As for our knowledge, the research work centering on the application of 2D UV-vis correlation spectroscopy in the study of mechanism remains limited. The work here not only verifies the feasibility of 2D UV-vis correlation spectroscopy, but also opens the application fields of it.更多还原