Two-Dimensional Infrared And Near Infrared Correlation Spectroscopic Study Of The Hydrophilic Polymers

This thesis centers on the application of two-dimensional infrared and near-infrared correlation spectroscopy(2DCOS) on the study of several hydrophilic polymers.2DCOS was proposed by Noda in 1986.Compared with conventional one-dimensional(1D) spectroscopy,2DCOS owns the high resolution and 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 1D spectra and has received wide applications in the different fields.In this thesis,the structure and performance of several hydrophilic polymers in the forefront of polymer science intercrossing with life science were characterized by 2DCOS, which included artificial intelligence materials and natural macromolecules.Moreover, the structure and property of bio-simulation material was also studied,which was supposed to be the direct investigation on the life activities.The thesis contains six chapters.Chapter one is the introduction of the whole research work.In chapter two,Thermo-sensitive phase transition behavior of poly(vinyl methyl ether)(PVME) in an aqueous solution during heating was investigated by Fourier transform infrared(FTIR) spectroscopy with attenuated total reflection(ATR) accessory,and Fourier transform near-infrared(FTNIR) spectroscopy.2D ATR analysis results indicate that hydrated C-H groups change prior to dehydrated C-H groups with increasing temperature around the phase transition, which suggests the existence of an intermediate state during the phase separation.2D NIR analysis results indicate that the dehydration of CH₂ groups occurs earlier than that of O-CH₃ groups.This result suggests that it is the change of the hydrophobic hydrocarbon chain conformation induced by heating that indirectly leads to the dehydration of the hydrophilic ether oxygen side groups.Thus,a two-step phase separation molecular dynamics mechanism during gradual heating has been established.When 0.5 M KC1 was added into a PVME aqueous solution,IR spectra showed that the phase transition temperature was reduced,and the features of 2DCOS did not change compared to PVME aqueous solution in the absence of KC1.The result indicates that the underlying phase transition mechanism itself was not altered by the presence of KC1,although the transition temperature is shifted.In chapter three,The states of sodium bis(2-ethylhexyl) sulfosuccinate(AOT) reversed micelles and of the water confined in the reversed micelles have been investigated by Fourier transform infrared spectroscopy with an attenuated total reflection(ATR) accessory.2DCOS revealed that a process of AOT molecules transforming from the trans conformation into the gauche conformation exists during heating.The quantitative analysis of the C=O stretching vibration band shows that the reversed micelles have the maximum size and lowest energy at the temperature of 38℃.The assignments of water confined in AOT reversed micelles in the O-H bending vibration region were concluded,which was considered to be the supplement for the former study results and laid a foundation of the studies in the next chapter.In chapter four,the state of acrylamide(AM) confined within the hydrophilic core of AOT reversed micelles has been investigated by Fourier transform infrared spectroscopy with an attenuated total reflection(ATR) accessory.2DCOS and curve fitting revealed that the acrylamide molecule tended to stick at the interface of the inverse emulsion at lower acrylamide-to-AOT molar ratio value(X);when X increased to some higher values,the acrylamide would tend to congregate in the micellar core.Therefore,it is important to choose the suitable initiator for the inverse emulsion polymerization under different experimental conditions.In chapter five,Temperature-dependent structural changes in hydrogen bonds in cellulose diacetate(CDA) were investigated by Fourier transform infrared spectroscopy(FT-IR).2DCOS in combination with moving-window technique was applied to analyze the overlapping O-H band due to various kinds of hydrogen bonds. In the temperature region of 35-100℃,the absorbed water in the hydrogen-bond matrix broke away,and the intra-chain hydrogen bonds in CDA changed accordingly. When temperature increased into a higher region,the inter-chain hydrogen bonds began to be weakened;both the inter-chain and intra-chain hydrogen bonds O-H groups change into free ones finally.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 1D spectra.Accordingly,we can distinguish the groups in different states and conformations.Thirdly,2DCOS 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.