Polarised Raman spectroscopy for the study of molecular orientation distributions in polymers

Polarised Raman spectroscopy is a vibrational spectroscopic technique that is used widely for the chemical and physical analyses of materials since it is both non-destructive and suitable for remote analysis. In particularly over the last 40 years, the technique has been developed and applied for the study of molecular orientation distributions in polymers. Compared to other analytical techniques, polarised Raman spectroscopy has the following advantages, (1) quantitative and precise measurement of molecular orientation distributions, and (2) study of these distributions in both the crystalline and amorphous phases. Knowledge obtained from the technique is of both academic and industrial interest to study relationships between microstructure and macroscopic physical properties in polymers. In this paper, polarised Raman spectroscopy is reviewed with regard to the study of molecular orientation distributions in polymeric materials. The basis of polarised Raman scattering is first described, and this is followed by the procedure for obtaining spectra. It is shown how Raman scattering intensities for different polarised scattering geometries can be interpreted to give parameters and functions representing quantitative measures of the degree of molecular orientation. Factors affecting the evaluation of these parameters are also summarised. Finally, the usefulness of the technique is demonstrated by practical applications including a study of molecular orientation distributions in poly(ethylene terephthalate) (PET) fibres. C 2006 Springer Science + Business Media, Inc.