Studies of polymer aging and polymer reactions by ramon spectroscopy : far-infrared spectra and potential energy surfaces of tetrahydrofuran-3-one /
Vibrational spectroscopy has been used for studying polymer
| Main Author: | |
|---|---|
| Format: | Thesis Book |
| Language: | English |
| Published: |
[Place of publication not identified] :
[publisher not identified] ;
1997.
|
| Subjects: | |
| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=736580431&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | Vibrational spectroscopy has been used for studying polymer materials and a small ring molecule. Raman spectroscopy was used for understanding subtle conformational changes of the bisphenol-A polycarbonate (BPAPC) polymer and to follow the reaction of trifluorovinyl ether monomers. Potential energy surfaces governing the conformational changes of tetrahydrofuran-3-one (THFO) were determined using far- infrared spectroscopy and fluorescence data. Raman difference spectroscopy (RDS) was used to measure small frequency shifts in the Raman frequencies of BPAPC when subjected to elongation or thermal aging. While only minor shifts were observed upon thermal treatment, the elongation resulted in several frequency shifts of -2.5 cm-' for the C-0 stretching at 1235 cm-' and of -0.78 cm-1' for the CH out-of-plane wag at 885 cm-'. This work demonstrates that conformational processes can be monitored using RDS and provides an indication of the types of process occurring. Raman spectroscopy was utilized for the kinetic analysis of the trifluorovinyl ether cylopolymerization to perfluorocyclobutane (PFCB) thermosets. The Raman band due to the C=C stretching at 1831 cm-' was used to monitor the extent of cure and the phenyl ring band at 1605 cm-' was utilized as the internal standard. The order of the reaction was determined to be 2.0 and the rate constants were obtained at various temperatures (130, 150, 170, 190 and 2101 C). The activation energy for the reaction was determined to be 24.6 kcal/mol. The far-infrared spectra of THFO show ring-bending (100 - 120 c@1), twisting (227 - 237 cm-'), difference (115 - 137 cm-1) and overtone (200 - 225 cm-') bands. A two- dimensional potential energy surface for the twisting and bending in the electronic ground state was determined and correspond to twisted conformations with twist angles of 2︢7'. No saddle points corresponding to bent structures are present for the surface. A potential energy surface for the Sl(n, pie) excited state, based on previous fluorescence excitation data, was calculated. The latter has an assumed barrier to planarity of 1400 cm-' and a barrier to pseudorotation of 880 cm-'. |
|---|---|
| Item Description: | Vita. "Major Subject: Chemistry". |
| Physical Description: | xi, 93 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilms Inc. |
| Bibliography: | Includes bibliographical references: pages 88-92. |