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Credit: Source IPC PAS, Grzegorz Krzyzewski

Science is wonderful and never ceases to surprise us. Curiosity, supported by modern devices used to pursue research, boosts the number of discoveries. No matter which hypothesis we have, sooner or later some researchers will investigate it. Recently, even a complex photopolymerization reaction has become powerless to counteract the powerful tools proposed by curious scientists. The new time-resolved NMR method combines time-resolved diffuse NMR and time-resolved non-uniform sampling demonstrated by researchers from the Institute of Physical Chemistry, Polish Academy of Sciences is one of them and makes the life of chemists easier. Let’s take a closer look at that unique method.

A little more than a century has passed since the technological revolution, and the tools that developed scientific observations are more sophisticated than ever. For example, consider light and its measurements. Simply saying, it is made of electromagnetic waves that have different wavelengths. Outside the visible range there are infrared rays that can be easily measured, for example, using coarse diffraction gratings in air. On the other hand, shorter waves can also be measured, while when air is absorbed, some UV rays will need a vacuum state to reduce this effect. Therefore, depending on the measurement objective, operating conditions can vary. Our knowledge of measurements continues to grow and is based on drawing general rules from experiments. How about monitoring chemical reactions? It seems easy for the different tools researchers use, while it all depends on the complexity of the processes being investigated. For example, designing new functional materials is not easy. It needs a comprehensive insight into the processes in which these materials are prepared or modified.

In many cases, the use of electromagnetic wave interactions with matter may be insufficient to explore some processes. Therefore, some other magnetic nature of the core can be used, as each one can be treated as small magnets. Thanks to the creation of the magnetic field by electrons orbiting the nucleus in an external magnetic field, the chemical composition or even the mechanisms of chemical processes can be determined.

Since the local magnetic field of the nucleus depends on the chemical character of the element, such as composition, molecular structure, or even interactions between molecules, the chemical composition of the samples can be examined using the technique of nuclear magnetic resonance, which is simply called NMR. It is one of the most comprehensive insights offering an in-depth look into molecular structures.

Recently, researchers from the Institute of Physical Chemistry, Polish Academy of Sciences, led by Dr. Mateusz Urbanczyk, proposed an enhanced NMR setup for detailed studies of complex chemical processes with high precision and real-time monitoring. Scientists have proposed combining two new, time-resolved NMR methods to allow the average diffusion coefficient of particular chemicals to be measured and the formation of reaction products simultaneously measured. The average mass of chemicals in the investigated process was determined based on these two methods, time-diffuse NMR and time-resolved non-uniform sampling. Even complex processes such as polymerization, photopolymerization or complexation can be explored in detail.

“In our work, photopolymerization was selected for di-anthracene-based systems. The system is very interesting to use as building blocks during polymerization which can be useful in designing diverse photofunctional materials” – says Dr. Urbanczyk

To demonstrate the potential of this technique, the photopolymerization of an aromatic derivative of dianthracene – nAnd then-bis(anthracen-9-ylmethyl)butane-1,4-diamine (H2banthbn) was examined, which shows the feasibility and advantages of the proposed method. Since photopolymerization depends on the experimental conditions and can undergo different pathways for different chemicals, due to its complexity, this type of chemical reaction was chosen.

“The synergy between both time-determined methods allows us to understand the photopolymerization process of H2banthbn. Using only diffusion methods, we will have a preliminary idea of ​​the average mass of the system, and obtaining information about particular n-mers will be close to impossible.” – Claims Dr. Urbanczyk

Consider both methods separately – based on the diffusion coefficient of a particular chemical, the number of a single molecule called mers changes during polymerization, which makes it difficult to determine the mechanism by measuring only such a parameter. It is difficult to follow the evolution of particular polymers but it is easy to determine the average mass of the reactant mixture. Therefore, it would be impossible to assess the kinetics of a chemical reaction, such as the lifetimes of diodes, pieces, or even larger molecules during the process.

Coupling this method with time-resolved sampling, in which the entire data is divided into specific groups and categorized, it is possible to attribute each peak recorded during complex operations in real time. The combination of different methods helped to provide a correlation between certain features of the studied system and information that could not be obtained when used separately.

Dr. Urbanczyk notes -”The comprehensive methodology presented was presented on a difficult system in terms of focus, line width and magnetic field. The presented approach is general and can be used for different types of chemical reactions, especially polymerization reactions and photoreactions. “

Thanks to the method proposed by Dr. Urbanczyk’s team, the use of both methods allows a better understanding of the mechanisms of chemical reactions, especially polymerization and photopolymerization, in real time, providing accurate data on the presence of specific molecules in the system.

This work was funded by the National Science Centre, Poland, under grant OPUS (2021/41/B/ST4/01286) and the research authors would like to thank the European Union’s Horizon 2020 Research and Innovation Program under Marie Sklodowska-Curie Grant Agreement No. 847413 and Project Established International Joint Program of the Minister of Science and Higher Education entitled “PMW” for the years 2020-2024, Agreement No. 5005/H2020-MSCA-COFUND / 2019/2.


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