Premium
Submolecular dynamics of amorphous polymers probed by two‐dimensional infrared (2D IR) spectroscopy
Author(s) -
Noda Isao,
Dowrey A. E.,
Marcott C.
Publication year - 1993
Publication title -
makromolekulare chemie. macromolecular symposia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.257
H-Index - 76
eISSN - 1521-3900
pISSN - 0258-0322
DOI - 10.1002/masy.19930720110
Subject(s) - polystyrene , infrared spectroscopy , amorphous solid , polymer , molecular physics , spectroscopy , chemistry , infrared , spectral line , dipole , wavenumber , materials science , analytical chemistry (journal) , chemical physics , crystallography , optics , physics , organic chemistry , quantum mechanics , astronomy
Two‐dimensional infrared (2D IR) spectroscopy was used to probe the submolecular dynamics of atactic polystyrene. 2D IR is a powerful analytical technique especially suited for the elucidation of localized motions of polymer segments. In 2D IR, a polymer sample is excited by a small‐amplitude oscillatory strain at a frequency in the acoustic range. The fluctuation of IR dichroism signals resulting from the strain‐induced reorientation of electric dipole‐transition moments is monitored with a time‐resolved spectrometer. Spectra defined by two independent wavenumber axes are constructed by applying a correlation analysis to such signals. The 2D spectra provide detailed information about the local dynamics of submolecular constituents of the system. From the sign of cross peaks in the synchronous 2D IR spectrum of glassy polystyrene, it is shown that the main‐chain backbone of polystyrene reorients in the direction of applied strain. Cross peaks in an asynchronous 2D IR spectrum reveal highly localized reorientational motions of phenyl side groups occurring more or less independently of the main‐chain realignment. In the glassy state, the phenyl ring tends to fold back along the main‐chain, indicating that there exists a highly constrained local distortion of side groups during deformation.