Inverse vulcanised polymers are a relatively newly discovered polymeric material. They are synthesized from a by-product of the petroleum refining industry – elemental sulphur, making these polymers of interest for low-cost, green chemistry. They have lots of industrial applications, ranging from water purification to highly refractive infrared optical components to batteries. Inverse vulcanised polymers are also sometimes recyclable.
However, the structure of these inverse vulcanised polymers isn't well understood. The use of commonplace analysis techniques like infrared spectroscopy and nuclear magnetic resonance to study the structure of these polymers is hindered significantly by their insolubility and transparency to infrared light. This presents a real challenge for researchers wanting to better understand these polymers. What alternative analytical techniques might be able to study the structure of these interesting polymers?
A team from the University of Liverpool, University College London, and the University of Bristol came to the CLF's Ultra facility to see if they could utilise Raman Spectroscopy to understand the structure of inverse vulcanised polymers. They found that they could use Raman spectroscopy to provide several key pieces of information about the polymers in a rapid and non-destructive way.
The fluorescent property of the polymers means that conventional Raman spectroscopy techniques 'fail' due to not avoiding or significantly reducing this fluorescence that interferes with Raman analysis. Therefore, the team's work focused on using different variants of Raman spectroscopic techniques that do reduce or avoid fluorescence, to compare them in the study of the inverse vulcanised polymers.
This research showed that Raman spectroscopy is a valuable technique in the analysis of inverse vulcanised polymers. The most of important of these structural discoveries was that Raman spectroscopy was able to determine not only the average sulphur rank of the polymer, but also the distribution of the population of different sulphur ranks present. This distribution has a tremendous impact on the polymer's properties, therefore the ability to quantify it is crucial to better understanding these inverse vulcanised polymers.
In the future, the team of researchers hope to find more techniques that can circumvent the fluorescence of the inverse vulcanised polymers and broaden the applicability of the computational aspects of the analysis to work for other polymer systems.
The publication “Raman Analysis of inverse vulcanised polymers" can be read in the RSoC's Polymer Chemistry journal.