We used confocal Raman microscopy for the elucidation of the morphology of semi-crystalline polymers modified with supercritical CO2 and to study polymorphism of a drug under a controlled environment. The major achievements of this research were:

  1. presentation of a combined methodology permitting the measurement of morphological gradients in polymer film by confocal Raman, point mapping Raman microscopy and FT-IR imaging
  2. observation of the morphological gradient in PET film after it has been subjected to supercritical CO2
  3. measurement of depth profiles for dyes impregnated into polymers from solution in supercritical CO2
  4. the quantitative data of the depth profiles of the dye in polymer was used a reliable dataset for modelling of diffusion process and interpretation of these data in terms of the mechanism of diffusion
  5. characterise and relate the morphology of the drug to the environment to which it was exposed

Overall, this research demonstrates that confocal Raman represents a very useful tool to analyse morphological gradients in polymers, polymorphism of drugs and to quantitatively study diffusion in polymer systems in a non-destructive manner which may be of great importance when mechanical sectioning would result in the adjustment of the polymer morphology and or distribution of components in the matrix. Furthermore, the combined application of FT-IR and Raman methods provided confidence in the reliability of the results due to general agreement between FT-IR imaging and Raman microscopic data obtained in this project. The use of supercritical CO2 prevents water pollution in dyeing of textiles and polymers and the application of confocal Raman microscopy, demonstrated in this project, is beneficial for optimisation of these processes.

Raman spectra from different depths

Key References

  • S. G. Kazarian and K. L. A. Chan, Confocal Raman microscopy of supercritical fluid dyeing of polymers, Analyst, 128, 0 (2003).
  • O. S. Fleming and S. G. Kazarian, Confocal Raman Microscopy of Morphological Changes in Poly(ethylene terephthalate) Film Induced by Supercritical CO2, Appl. Spectrosc. 58, 390 (2004).
  • K. L. A. Chan, O. S. Fleming, Kazarian S. G., Vassou D., Chryssikos G. D., Gionis  V. Polymorphism and devitrification of nifedipine under
    controlled humidity: a combined FT-Raman, IR and Raman microscopic investigation     J. Raman Spectrosc. 35, 5, 353 (2004).
  • O. S. Fleming, K. L. A. Chan, and S. G. Kazarian, FT-IR imaging and Raman microscopic study of poly(ethylene terephthalate) film processed with supercritical CO2, Vib. Spectrosc., 35, 3 (2004).
  • O. S. Fleming, F. Stepanek, and S. G. Kazarian, Dye Diffusion in Polymer Films Subjected to Supercritical CO2:Confocal Raman Microscopy and Modelling, Macromol. Chem. Phys. 206, 1077 (2005).
  • O.S. Fleming, S. G. Kazarian, E. Bach, W. Shollmeyer, Confocal Raman Study of PET fibres dyed with Supercritical Carbon Dioxide: Dye Diffusion and Polymer Morphology, Polymer, 46 (2005) 2943-2949.
  • Qian H., Kalinka G., Chan K. L. A., Kazarian S. G., Greenhalgh E. S., Bismarck A., Shaffer M. S. P. Mapping local microstructure and mechanical performance around carbon nanotube grafted silica fibres: methodologies for hierarchical composites Nanoscale 3 (2011) 4759-4767 (doi)
  • Actis P., Tokar S.,  Clausmeyer J., Babakinejad B., Mikhaleva S., Cornut R., Takahashi Y., Novak P. , Shevchuck A.,  Dougan J. A., Kazarian S. G., Gorelkin P., Unwin P. R., Schuhmann W., Klenerman D., Sviderskaya E., Korchev Y. Electrochemical nanoprobes for single-cell analysis ACS Nano (2014) 8(1), 875–884. (doi)
  • Ewing, A. V. , Wray P.S, Clarke G. S, Kazarian S. G. Evaluating drug delivery with salt formation: drug disproportionation studied in situ by ATR-FTIR imaging and Raman mapping Journal of Pharmaceutical and Biomedical Analysis (2015) 111, 248−256