To design new materials, scientists must have a clear understanding of the chemical reactions or processes that occur when creating these materials. Researchers supported in part by the PD2PI project have now combined two new NMR-based monitoring methods, providing insight into complex chemical processes such as photopolymerization. Their findings are described in the Journal of the American Chemical Society.
In polymerization processes, where small molecules called monomers combine to form a very large chain or 3D network called a polymer, knowing what is happening during the reaction would make it much easier to tune the product development process. This is also true for photopolymerization processes that use visible or ultraviolet light to induce a polymerization reaction that forms a polymer structure.
Two NMR-based methods for comprehensive monitoring
However, how do you get detailed information about the molecular structure of various solids and liquids? One of the most comprehensive ways is to perform NMR measurements. For this study, the researchers combined two NMR-based reaction monitoring methods that had never been used together to analyze a particular system: time-resolved diffusion NMR and time-resolved non-uniform sampling.
The first method measures the average diffusion coefficient of particular chemicals, while the second allows monitoring of product formation. Their results indicate that combining the two methods is an excellent way to comprehensively monitor light-curing.
To demonstrate the potential of their approach, the team avoided using an overly simplified model to monitor, choosing instead to photopolymerize an aromatic bis-anthracene derivative – N,N-bis(anthracen-9-ylmethyl) butane-1,4-diamine (H2banthbn). “
In our work, a photopolymerization of bis-anthracene-based systems was chosen. The system is very interesting for the use of building blocks during the polymerization which can be useful for the design of various photofunctional materials”, explains the lead author of the study, Dr. Mateusz Urbańczyk from PD2PI, project coordinator of the Institute of Physical Chemistry of the Polish Academy of Sciences. .
The simultaneous use of the different methods made it possible to establish a correlation between the particular characteristics of the system and the information that could not be obtained when the two methods were used separately. The authors explain in the article that “the synergy between the two time-resolved methods allows us to understand the photopolymerization process of H2banthbn. Using only the diffusion methods, we would only have a rough idea of the average mass of the system, and getting information about particular n-mers would be next to impossible.”
“The HSQC data allow us to track the concentration changes of each n-mer, giving us some pretty compelling information about the system. That being said, assigning the peaks without confirming the scattering data would be ambiguous. The use of the two methods allow us to have certainty about the assignment and, therefore, to better understand the system.”
“Finally, the complete methodology presented was demonstrated on a challenging system in terms of concentration, linewidths and magnetic field. The approach presented is general and can be used for different types of chemical reactions, in particular the reactions of polymerization and photoreactions.
Development of a new terminal functionalization technique in polymer synthesis
Kristina Kristinaityte et al, Deeper Insight into Photopolymerization: The Synergy of Time-Resolved Nonuniform Sampling and Diffusion NMR, Journal of the American Chemical Society (2022). DOI: 10.1021/jacs.2c05944
Quote: Researchers combine two NMR-based methods to understand the photopolymerization process (2022, October 24) Retrieved October 25, 2022 from https://phys.org/news/2022-10-combine-nmr-based-methods- photopolymerization.html
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