Investigation On The Interactions Between Polymers And Different Kinds Of Chemical Mediums By Infrared And Two Dimensional Correlation Infrared Spectroscopy

This work is concentrating on discussing the interactions between polymers and some kinds of chemical mediums, and the change of structures of polymers with the existence of chemical mediums.Up to now, solvents like supercritical fluids and ionic liquids were newly discovered and studied.Owing to the excellent physical and chemical properties, nontoxic nature, good solvency, and feasible to be recycled, they are showing a promising prospect in the scientific researchs and the industrial applications.Being utilized into the fields of polymers, especially as new kinds of solvents or functional additions, they would probably improve the structure and property of a polymer and also contribute in designing new materials.To carry on investigations and studies on the interactions existed between polymers and the mediums, is of great benefit to the systhesis and invention of advanced polymer materials.Fourier transform infrared spectroscopy (FTIR) and two-dimensional correlation infrared spectroscopy (2DIR) are two of the most useful methods in studying the interactions because of their perfect ability to observe the variation of structures of polymers and the hydrogen bonding interactions as well.In this work, FTIR and 2DIR are applied to study the supercritical carbon dioxide (scCO2) induced crystalline transformation of isotactic polybutene,the micro-structure of the material composed of ionic liquids([Bmim][BF4])and polystyrene, and the variation of hydrogen bonding interactions between water and ionic liquids([Amim]Cl and [Bmim]Cl) during the water vaporization.The whole paper is composed of five chapters. An introduction of the entire work is provided in Chapter I.Herein, a brief introduction on the chemical mediums and their applications in the field of green chemistry and polymer processing is offered.Supercritical fluids (especially scCO2) and ionic liquids, as newly improved solvents with proper properties for green chemistry, are well recommended. Besides, detailed information about FTIR and 2DIR is attached, acting as a background for understanding the investigation methods in the following researchs.In ChapterⅡ, in-situ Fourier transform infrared spectroscopy (FTIR) and two-dimensional correlation spectroscopy (2DIR) are used to observe and investigate the crystallization behaviour of iPB in scCO2 and compressed CO2.It is found that the solid-solid crystalline transformation of isotactic polybutene-1 (iPB-1)from tetragonal formⅡto hexagonal form I could be accelerated by scCO2.Based on the transform sequence given by 2DIR analysis, this transformation of helical chain structures is found to be initiated with the motion of side chains and followed by the movement of main chains.It is speculated that the motion of polymer chains was enhanced with the diffusion of CO2.Also this crystalline transition is observed even in compressed CO2, suggesting that CO2 could also diffused into polymer under high pressure near the critical pressure.This diffusion of CO2 is indicated by the growth of IR bands being assigned to the stretching vibration of C-O.A further investigation on the mechanically heating and freely cooling of iPB provides more evidences on the process of structure transition. The result implies that the nucleus of tetragonal form II formed in the melt is not affected by the existence of scCO2, but the crystallization temperature become obviously lower.ChapterⅢpresents the study on the micro-structure of the material composed of ionic liquids([Bmim][BF4]) and polystyrene.The intermolecular interaction and distribution of components in [Bmim][BF4]-based polystyrene composite membrane which is composed of 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim][BF4]), poly(1-(2-methyl acryloyloxyundecyl)-3-methylimidazolium bromide) (poly(MAUM-Br)) and polystyrene is investigated by FTIR and 2DIR in this study. A proposed model about the structure of this composite material is presented, and a sketch map about the local distributions of components is provided. In this model, alkyl chains in [Bmim][BF4],poly(MAUM-Br) and polystyrene in this system was supposed to form a polymeric network through aggregation or co-polymerization. Cations of ionic liquids separate into the polymer network, while anions are kept mainly through the Coulomb force and partially by the hydrogen bonding between cations and anions. To support this model,FTIR has provided some hints on theπ-πinteraction existing in this complex material between the imidazole ring of ionic liquids and the benzene ring of polystyrene, based on the discovery of the shift of IR absorption bands assigned to the C-C stretching vibrational mode.The sequential order of the responses from different chemical groups towards the variation of temperature is calculated by 2DIR, and the results suggest how different components distributed in this [Bmim][BF4]-based polystyrene composite membrane.In the appended chapter, the dynamic variations of hydrogen bonding interactions existed in the mixture of ionic liquids([Amim]Cl) with water during the heating and isothermal process are investigated by Fourier transform infrared spectroscopy (FTIR), near infrared spectroscopy (NIR) and two-dimensional correlated infrared spectroscopy (2DIR). FTIR and NIR are applied to acquire a series of temperature-dependent or time-dependent spectra during the whole process:heating from room temperature to a constant temperature and then let water vaporize under this constant temperature.By integrating the peak area of v(O-H) and v(C-H) region on all of the FTIR spectra, a monotone decrease of intensities of v(O-H) and a "V-shaped" dynamic change of intensities of v(C-H) are observed.In a further investigation on the "V-shaped" dynamic change of v(C-H),2DIR is utilized to distinguish individual absorption bands on FTIR and NIR spectra and bands assigned to v(O-H) and v(C-H) involved in different kinds of hydrogen bonds are illuminated. Based on the sequence of variation order given by 2DIR analysis, and the supports from observations on FTIR and NIR spectra, the dominating change of interactions in the mixture during the heating process is found to be different from that of the isothermal process.It is then concluded that the "V-shaped" dynamic change of v(C-H) is brought by the reduction of hydrogen bonds between cations and water in the heating process, and the rebuilding of hydrogen bonding interactions between cations and anions in the isothermal process.Another ionic liquid [Bmim]Cl is also studied by the same procedure, and a similar result on the dynamic variation of interactions in this ionic liquid-water mixture is obtained.Chapter IV shows a conclusion of the whole work. FTIR and 2DIR, as the main methods for measurement, are utilized to discuss the interaction of the existence of chemical mediums on the structures and physical properties of polymers.The significance of this study is to provide theoretical background for the industrial application of scCO2 in the crystalline transformation of polymers, and the applications where ionic liquids acted as the chemical mediums.