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Vibrational spectroscopic study and structure calculation for model compounds and polyurethanes
Abstract
Vibrational spectroscopy has been applied to the study of a small ring molecule, three model urethane compounds and Poly (4,4$\sp\prime$-bis(6-${\rm hydroxyhexyloxy}$)biphenyl-co-2,4-toluenediisocyanate) (2,4-TDI polyurethane) systems. The computer program, POLYGRAF, was used to estimate the stability of some conformers of the three model compounds. Grazing angle microscopy was used to study the surface structure of thin films of polyurethane. The synthesis, far infrared spectra, temperature dependent mid-infrared spectra and the Fourier transform Raman spectra are reported for polycrystalline samples of three model urethanes, 1,3-phenyl di(methyl carbamate) (1,3-PDI based urethane), 2,6-toluene di(methyl carbamate) (2,6-TDI based urethane), and 2,4-toluene di(methyl carbamate) (2,4-TDI based urethane). Geometry optimization is reported for phenyl methyl carbamate both by ab initio and molecular mechanics methods, and of the three model urethanes by molecular mechanics methods using the Dreiding I force field. The results suggest that in isotropic surroundings only a very small number of the many possible conformers of the urethane groups in these molecules contribute appreciably to the structure. In this polyurethane research, the intermolecular interaction, morphology and microstructure of 2,4-TDI polyurethane are studied. Four bands were found in the carbonyl stretching region in this polyurethane film. The bands were assigned based on temperature dependence and solution spectra. A molecular interpretation of hydrogen bonding behavior is given. The temperature dependence of infrared spectra of the 2,4-TDI polyurethane films are also reported in chapter 3 together with some kinetic data. A very thin film was prepared to study the surface behavior of 2,4-TDI polyurethane. An infrared spectrum was obtained by grazing angle reflection-absorption. The results suggest that 2,4-TDI polyurethane has a layered structure and that most of the NH groups and carbonyl groups are free on the surface. The infrared spectra of 1,4-cyclohexadiene and 1,4-cyclohexadiene-3,3,6,6-d4 were recorded in the gas phase at room temperature. From the CH stretching to the CD stretching, the frequency shift is 753 cm$\sp{-1}$. The CH$\sb2$ scissor was found at 1440 cm$\sp{-1}$ and the CD$\sb2$ scissor was found at 1071 cm$\sp{-1}$, the frequency shift is 369 cm$\sp{-1}$. From CH$\sb2$ rock to CD$\sb2$ rock, the frequency shift is 80 cm$\sp{-1}$ only.
Subject Area
Analytical chemistry
Recommended Citation
Wang, Qiong, "Vibrational spectroscopic study and structure calculation for model compounds and polyurethanes" (1992). Doctoral Dissertations Available from Proquest. AAI9233174.
https://scholarworks.umass.edu/dissertations/AAI9233174