Expert Insight: Raman microscopy: Comprehensive characterization of polymers

Learn how to obtain accurate, non-destructive, information on polymers in this on-demand webinar

16 Feb 2021

HORIBA Scientific
Thibault Brulé, Raman Application Scientist, HORIBA

During the 1940s and 1950s, polymer chemistry became increasingly efficient and also more complex, offering a multitude of new materials. Polymers are now unavoidable in many application fields.

Understanding the polymerization process, polymer structure, or identifying defects in final products is therefore very important for many laboratories. Raman microscopy is one of the most powerful techniques for obtaining accurate, non-destructive, information when it comes to polymers. 

In this on-demand SelectScience® webinar, learn how Raman microscopy is a key technique for polymer studies using various application examples. Plus, discover how to solve daily work changes with HORIBA micro-Raman and QScan functionalities.

Read on for highlights from the live Q&A session or register to watch the webinar at any time that suits you. 

The following questions were answered by Raman Application Scientist, Thibault Brulé, of HORIBA Scientific.

Q: In slide 21, you spoke about a smart sampling algorithm. Can you get really high-quality Raman images in a short amount of time from it?

TB: We have a new tool that will be very useful for fast mapping in Raman. In this case, based on a video contrast image, the software will automatically recognize and focus on the different features of interest in the mapping area. So very quickly, in just two minutes, you will have your first idea of the image, giving you an idea of the distribution of the different chemicals, or of the different crystal phases, which will then improve over time to give greater detail. 

Q: Do you have any Raman techniques that can work in-line for manufacturing processes?

TB: Raman is a form of spectroscopic analysis. Therefore, it can merge in-line in the manufacturing process because acquisition time can be down to a few tenths or hundredths of a millisecond. As you can do a Raman spectrum very quickly, you can rapidly generate an idea of the molecule and the characterization of your polymer, so you can do some in-line measurements. Moreover, with some systems, like the MacroRAM, our benchtop system, we can couple with some fibers to an external probe, as a non-contact probe. In this case, it is easy to imagine placing this probe on the top of a film during manufacturing to check the criteria during the production process. Overall, yes, Raman can be easily applied in-line to a manufacturing process using a benchtop system coupled with fiber probe capability.

Q: Can Raman be used to give information about pendants?

TB: Most of the compounds that would be given from Raman would be from the backbone chain. However, if the pendant includes some dye, then yes, it can give some Raman signal and you will see it in the spectrum, not only the backbone chain spectrum but also the pendant’s contribution. Although, the pendant’s contribution will be reduced compared with the backbone chain. 

Q: Regarding polymerization studies, could Raman be used for vulcanization? Is it difficult with FTIR?

TB: Yes, Raman can be useful for vulcanization. You can do direct measurements using a contact probe, but also a non-contact probe. It can be done through any polymerization chamber, directly through a window or using a probe directly in the chamber to make the analysis in contact with the polymer.

Q: Would highly crystalline cellulose, MCC, look different from pure, fully amorphous cellulose?

TB: Yes. The spectrum will be different, the bands in the spectra will be different, and the bandwidth of the bands will be different. The band positions also. Therefore, it is possible to determine different levels of cellulose crystal phases based on the Raman spectrum.

Q: Going back to the spatial distributions on slide 23. For a long time of exposition, there is some material ablation. What is the spot size of mapping?

TB: The acquisition time was not so long in that case because there is no ablation from the laser. It is a nondestructive technique, it will just interact with the material. For the spot size of the mapping, it depends on how you work. The spot size that you can achieve under the microscope is down to the limits of resolution. It means that with a high-resolution map you can achieve a spot size of mapping which is below 1 micron. For example, it can be 500 nanometers, in which case you can see very small details.

Q: How long does a 3D spectrum take to acquire?

TB: In 3D mapping, you will scan multiple points over the depth. Therefore, it can take a short time if you do just a few points of measurement. But if you are looking to investigate the small details, for which you need more points of measurement, it will take a longer time. It will depend on the level of detail that you are looking for. Typically, a 3D map will take around 10 to 30 minutes.

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