Uniplanar orientations as a tool to assign vibrational modes of polymer chain

The occurrence of films with different uniplanar orientations of the crystalline phase, which allows an experimental evaluation of the orientation of transition moment vectors (TMV) of vibrational modes corresponding to most infrared peaks were studied. It was also studied that this information allows the difficult task of assignment of modes to vibrational peaks of complex polymer helices to be afforded. The quantum mechanical calculations were carried out with the CRYSTAL06 code¹⁰ by adopting the B3LYP functional together with a Gaussian Type all-electron 6-3lG(d,p) basis set as level of theory. The resulting computed frequencies were scaled by a factor of 0.972 to best fit the experimental values in the selected region in order to compare the computed and the experimental spectra. A graphical representation of the IR computed spectrum was obtained by using the calculated JR intensities and a Lorentzian profile.