Project title: Toward a quantitative description of the free-radical photopolymerization behaviour of novel one-component photoinitiators with significantly improved photoinitiating ability under visible light, obtained by expanding the conjugated bond system.
Principal investigator: mgr inż. Andrzej Świeży
Obtained funds: 210 000 PLN
Start day: 2023-01-09
End day: 2026-01-08
NCN – Polish National Science Centre
Prof. Jacque Lalevee from the Institut Universitaire de France - Institut de Science des Matériaux de Mulhouse (IS2M)
Short disctoption of the project:
The utilization of light to induce chemical transformations to create, rearrange, or cleave chemical bonds provides a powerful toolset for synthesizing polymeric materials. Therefore the primary goal of this research project is to synthesize and determine the spectroscopic characteristics of new photo-cleavable compounds based on acetophenone type (e.g., 2,2-dimethoxy-2-phenylacetophenone (DMPA)) species) which will be able to form radicals via a direct cleavage process (Norrish type I) during the absorption of light from the visible region of the electromagnetic spectrum. The critical research goal will be to determine the factors and how they affect the efficiency of radicals in newly obtained free-radical photoinitiators and how these initiators can be improved through structural modification. Therefore the effect of this project will be the development of efficient homocleavage moieties for the role of free-radical photoinitiators and the development of a set of rules for the design of new, more efficient light-sensitive molecules than those are used currently.
Therefore, one of the essential aims of the proposed project is to show how the individual features of photoinitiators can be combined to achieve an efficient polymerization. For this reason, photopolymerization kinetic measurements will be performed, including the effects of absorption properties, dissociation quantum yields, light intensities, irradiation wavelengths, penetration depth and the influence of the oxygen inhibition process as a side reaction. The systematic step-by-step analysis of photoinitiators will understand the interplay of free-radical photoinitiators' spectroscopic properties and the reactivity of the primary radicals towards the monomer. As a result, obtaining a balanced combination of all these factors will be crucial for achieving optimal initiation performance. A key goal for basic research aimed at the experimental clarification of the issues raised will not only contribute to a better understanding of the mechanisms of action of the initiators themselves. However, it will also enable the development of guidelines for designing new, more effective initiating systems for cationic polymerization. This aspect is crucial and requires sophisticated thorough study.
The general research plan is divided into two main parts, synthesis of new compounds and characterizing them in terms of their photochemical and photophysical properties as well as their ability to photoinitiated free-radical polymerization of monomers.
1) Chemical compounds selected for the photoinitiators will be synthesized and studied.
2) A detailed study of photochemical, photophysical, and electrochemical properties of the developed radical initiators and their components will be carried out.
3) A comprehensive study of the kinetics of the free-radical photopolymerization initiated with photoinitiators will be performed using photo-DSC, photo-rheology, and real-time FTIR.
4) The reactive species involved in the free-radical polymerization process by laser flash photolysis, time-resolved fluorescence and phosphorescence, and electron spin resonance spectroscopy will be identified.
5) Cytotoxicity testing includes MTT tests, flow cytometry analyses and the colorimetric LDH assay.
This fundamental research will be aimed not only at the elucidation of the reaction mechanisms by which these photoinitiators work but also at determining criteria for the design of new, more effective, and sensitive free-radical photoinitiators that will provide additional advantages associated with the environmental and safety issues in free-radical photo-initiating systems, which are currently on the mark Most efficient photoinitiators will be examined in terms of the possibility of using them in 3D printing. The studies will be carried out on systems containing different monomers. The printed objects will be compared concerning resolution, durability and colour.