| 초록 |
This study introduces the application of two novel methods to determine the glass transition temperature (Tg) of an Langmuir-Blodgett (LB) film of poly(tert-butyl methacrylate) (PtBMA) from external reflectrion FTIR spectra. Two-dimensional (2D) mapping of the first derivative of absorbance valuges against temperature over the wavenumber range 1100 - 1300 cm-1, which contains spectral features that are very sensitive to conformational changes, enables us to determine Tg. Principal component analysis (PCA) was successfully applied to determine Tg by finding the point with the largest change from the PC2 and PC3 scores of the temperature-dependent FTIR spectra that preserves almost of all structural information of the original data. Additionally, the loading vectors of PCA were found to give valuable insight into the molecular level phenomena asociated with the glass transition process. To gain more details about the polymer chain mobility, 2D correlation analysis was performed on two sets of spectra colleced above and below Tg. The characterization of Tg of an LB film of PtBMA probed at the molecular level and the overall reorientation of functional groups sensitive to conforamtional changes over two temperatures, above and below Tg, will be discussed. |
