Master of Science (MS)
The first chapter gives a brief introduction into thermosensitive polypeptoids and C−H∙∙∙O hydrogen bond. A brief discussion on FTIR and its lineshpe function is also included. The theoretical background and spectral features about 2DIR spectroscopy are briefly discussed in this part. In Chapter 2, we conducted a series of studies on the linear and cyclic co-polypeptoids having the same composition, but different architecture. It is concluded that the difference in the thermal response of the linear and cyclic polymers is caused by the presence of the initiator group. In addition, DLS, NMR, and IR spectroscopy studies indicate that both polymers have very similar structure at temperatures below and close to the phase transition temperature. Our experiments reveal that the conformation of the polymer backbone is crucial for determining the phase transition temperature. The proposed mechanism is different from other previously studied thermo-responsive polymers where the hydration of the polymer is the determining factor. The third chapter gives a spectroscopic evidence for the presence of C−H∙∙∙O hydrogen bonding. In this chapter, it was found that the amide I band of N-methylacetamide (NMA) in chloroform solution contains two components. After ruling out the possibilities of dimer formation, conformational isomerization, and dipole-dipole interaction, the formation of hydrogen bond between NMA and the solvent was proposed. Corresponding studies on its derivatives, N-ethylpropionamide (NEPA) and N-isopropyl propionamide (NIPA), also corroborate the idea of hydrogen bonding. Moreover, that the amide I band of NMA in CHCl3 solution is composed of two transitions is also confirmed by a theoretical study.
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Ma, Jianbo, "Spectroscopic Investigation on the Molecular Mechanism of the Phase Transition of Thermosensitive Polymers" (2017). LSU Master's Theses. 4553.