Premium
A Raman confocal microspectroscopic study on azopolymer holographic diffraction gratings: Photo‐ and mass transport‐induced effects on the molecular orientation
Author(s) -
Labarthet F. Lagugné,
Buffeteau T.,
Sourisseau C.
Publication year - 1999
Publication title -
macromolecular symposia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.257
H-Index - 76
eISSN - 1521-3900
pISSN - 1022-1360
DOI - 10.1002/masy.19991370109
Subject(s) - materials science , azobenzene , holographic grating , raman spectroscopy , optics , chromophore , diffraction efficiency , grating , amorphous solid , raman scattering , diffraction , holography , molecular physics , polymer , diffraction grating , optoelectronics , chemistry , physics , crystallography , organic chemistry , composite material
Using the confocal microspectrometric technique we have recorded various resonance enhanced polarized Raman spectra from the surface profile of a permanent holographic diffraction grating prepared by interfering two circularly contra‐rotating polarized laser beams on a thin amorphous copolymer film containing azobenzene moities (pDRIM‐co‐MMA). Different theoretical equations of the Raman scattering intensities, including a treatment taking account for the effect of the high numerical aperture objective, are thus derived. Calculations and simulations of these equations allow for the first time to extract the second
and fourth
coefficients of the chromophore orientation function in the various regions and to obtain the corresponding information entropy distribution functions. We then discuss both contributions of the photo‐ and mass transport‐ induced effects in the grating formation mechanisms and confirm the existence of a significant dye concentration gradient (δN/N = 5.1±1.1%) in between the top and bottom regions. All the results are consistent with the model of a viscoelastic flow of the polymer involving large pressure gradients and translational diffusion dynamics.