Raman and Infrared Imaging of Dynamic Polymer Systems

Abstract

This work reviews principles of Raman and infrared imaging, as well as applications of the art to understand physiochemical phenomena in polymer systems. Image sequences may be assessed in terms of spatial or spectral changes that occur over time, either within a specific region or across the field of view. As such, the methods have enabled the analysis of diffusion and dissolution processes at polymer interfaces, drug release from polymer matrices, and structural transitions among others. Despite analytical limitations imposed by resolution (spectral or spatial) and sample preparation, Raman and infrared imaging are powerful tools for relating performance attributes to molecular‐level characteristics.magnified image

Electron-beam exposure mechanisms in hydrogen silsesquioxane investigated by vibrational spectroscopy and in situ electron-beam-induced desorption

“…18 The techniques are complementary: Raman scattering is sensitive to modes that result in a change in molecular polarizability upon vibration, while IR spectroscopy is sensitive to modes that result in a change in molecular dipole moment; both are sensitive to, and therefore reporters of, the local environments surrounding the active bonds. However, Raman spectroscopy has a spatial-resolution advantage over FTIR; diffraction-limited spot sizes below 500 nm are readily achievable, compared to 8-10 µm in FTIR.…”

Applications of FTIR Spectroscopic Imaging in Pharmaceutical Science

“…A large particle seen in an image may in fact not be a large particle, but instead consist of two separate particles at different depths that slightly overlap in the path of the beam as shown in Figure 10.2. Nonetheless, transmission imaging has been successfully applied to many materials [15][16][17].…”

FT‐IR Imaging in ATR and Transmission Modes: Practical Considerations and Emerging Applications

“…In order to maintain adequate throughput of light, often the sample must be kept thin ∼10 μm thick. Nevertheless, in some cases, it is convenient to use transmission mode FT-IR imaging and the approach has made important contributions to the study of complex systems, particularly for biomedical and tissue imaging [12][13][14][15][16][17][18][19] and in many polymer applications [20][21][22][23][24] It is undoubtedly simpler to map transmission mode FT-IR measurements compared with that of ATR in order to generate images. Transmission mode FT-IR spectroscopy can be coupled with single-element detectors to provide an average spectrum from the sample or with FPA detectors to produce chemical images of the material through which the IR light passes.…”

“…ATR FT-IR spectroscopic imaging has been shown to be a valuable asset in such studies and has allowed insight to be gained into many processes including drug polymorphism [30,34,82]; the effect of polymer swelling [9], pH (of the dissolution media) [79], the micro-environement [83], or the drug loading and sample preparation [73,84] on drug release. Apart from the ability to acquire thousands of IR spectra simultaneously within a matter of seconds, thus allowing dynamic systems to be studied for FT-IR imaging with the FPA detector [23,30,38], this type of study is made possible with the ATR approach allowing the study of samples in aqueous environments. Apart from the ability to acquire thousands of IR spectra simultaneously within a matter of seconds, thus allowing dynamic systems to be studied for FT-IR imaging with the FPA detector [23,30,38], this type of study is made possible with the ATR approach allowing the study of samples in aqueous environments.…”