Optical anisotropy Raman response of polyethylene terephthalate strained thin films

We investigate the optical-anisotropy response of uniaxially strained polyethylene terephthalate (PET) films by Raman spectroscopy. A ribbon sample was mechanically strained in a stretching press and the associated Raman modes were spectrally collected and compared with those of its relaxed state. A classical theoretical approach for the intensity of the Raman response, is used to describe through angle-dependent Raman spectroscopy, the change of symmetry of the polymer, as a result of the mechanically induced strain. Results reported here demonstrate the potential of this spectroscopy as a probe capable to detect the molecular orientation of PET strands and the tensile variations, though a simple classical analysis of the Raman modes.