Acrylates are an industrially significant group of polymers with wide applications in coatings, textiles, and cosmetics. The presence of a C-C double bond located adjacent to a carbonyl makes acrylates highly reactive, especially in radical reactions. Electron-beam (EB) polymerization is a radiation polymerization method in which accelerated electrons are used to form radicals on the monomer species. EB is advantageous compared to other methods of polymerization in that it does not require the use of volatile solvents or free-radical initiators. However, EB results in indiscriminate hydrogen abstraction, eliminating the usefulness of common reference peaks used in Raman spectroscopy for conversion measurements in these systems. Thus, to calculate conversion in EB-polymerized systems using Raman spectroscopy, a highly stable reference group such as an aromatic ring is required. However, most industrially relevant acrylates, such as tri-methyl propyl triacrylate (TMPTA) and iso-bornyl acrylate (IBOA), lack phenyl groups. In such systems, an external reference molecule could be added to a reaction mixture, providing a stable reference group for conversion calculations. This work aims at validating pyrene as an external reference for conversion calculations in EB-polymerized systems using Raman spectroscopy. Pyrene was selected as an external reference due to its high aromaticity, distinct Raman peaks, and solubility in acrylate monomers. First, a neat calibration curve was created by dissolving varying amounts of polystyrene in styrene and calculating “conversion” via the system’s internal reference of the pendant aromatic ring. The feasibility of using the aromatic ring in styrene as a reference structure has been verified in previous work. This neat calibration curve was then compared to a pyrene-spiked calibration curve, in which the external pyrene reference was used for “conversion” calculations. Both calibration curves yielded similar “conversion” results. After validating that pyrene could be used in a non-reactive system that simulates polymerization, pyrene was added to TMPTA formulations undergoing thermal polymerization with the free-radical initiator AIBN. The pyrene external reference yielded similar conversion results compared to a neat system using the internal reference under a given set of reaction conditions. However, even though similar final conversions were achieved, pyrene affected the reaction time of the system, requiring further study of pyrene’s impact on reaction kinetics.
