Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2020 Apr 28;25(9):2063.
doi: 10.3390/molecules25092063.

Coumarins as Powerful Photosensitizers for the Cationic Polymerization of Epoxy-Silicones under Near-UV and Visible Light and Applications for 3D Printing Technology

Mira Abdallah  1   2   3 , Akram Hijazi  3 , Frédéric Dumur  4 , Jacques Lalevée  1   2
Affiliations

Coumarins as Powerful Photosensitizers for the Cationic Polymerization of Epoxy-Silicones under Near-UV and Visible Light and Applications for 3D Printing Technology

Mira Abdallah et al. Molecules. .

Abstract

In this study, eight coumarins (coumarins 1-8) are proposed as near-UV and blue light sensitive photoinitiators/photosensitizers for the cationic polymerization (CP) of epoxysilicones when combined with 4-isopropyl-4'-methyldiphenyliodonium tetrakis(pentafluorophenyl)borate (IOD). Among these coumarins, four of them (coumarins 1, 2, 6 and 8) have never been reported in the literature, i.e., these structures have been specifically designed to act as photoinitiators for silicones upon near UV and visible irradiation. Good final reactive epoxy function conversions (FCs) and also high rates of polymerization (Rp) were achieved in the presence of the newly proposed coumarin-based systems. The polymers generated from the photopolymerization of epoxysilicones can be considered as attractive candidates for several applications such as: elastomers, coatings, adhesives, and so on. The goal of this study focuses also on the comparison of the new proposed coumarins with well-established photosensitizers i.e., 1-chloro-4-propoxythioxanthone (CPTX), 9,10-dibutoxyanthracene (DBA) or some commercial coumarins (Com. Coum). As example of their high performance, the new proposed coumarins were also used for laser write experiments upon irradiation with a laser diode at 405 nm in order to develop new cationic 3D printing systems.

Keywords: LED; cationic polymerization; coumarin; epoxy-silicone; light-emitting diode; photoinitiator; photopolymerization.

PubMed Disclaimer

Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Chemical structures of the synthesized coumarins 1–8 used in this research.
Scheme 1
Scheme 1
Synthetic routes to coumarins 3 and 7 and compounds A–C.
Scheme 2
Scheme 2
Synthetic routes to coumarins 1, 2, 4–6 and 8.
Figure 2
Figure 2
UV-Visible Absorption Spectra of Coumarins Studied in Acetonitrile: (A): (1) Coumarin 1; (2) Coumarin 2; (3) Coumarin 3; (4) Coumarin 4; (5) Coumarin 5; (6) Coumarin 6. (B): (7) Coumarin 7; (8) Coumarin 8; (9) Com. Coum 1; (10) Com. Coum 2; (11) Com. Coum 3; (12) Com. Coum 4, respectively.
Scheme 3
Scheme 3
Proposed Photochemical Mechanisms for Cationic Photopolymerization Processes Initiated by Coumarins [13].
Figure 3
Figure 3
Polymerization profiles (epoxy function conversion vs. irradiation time) for thin epoxy-silicone films (thickness = 25 μm) under air, upon irradiation with the LED@405 nm, using different two-component photoinitiating systems: (A) PI/IOD (0.05%/1% w/w): (1–8) Coumarin 1-Coumarin 8/IOD; (9) Com. Coum 2/IOD and (10) Com. Coum 4/IOD, respectively. (B) PI/IOD (0.1%/1% w/w): (1–8) coumarin 1-Coumarin 8/IOD; (9) Com. Coum 2/IOD; (10) Com. Coum 4/IOD; (11) CPTX/IOD and (12) DBA/IOD, respectively. The irradiation starts at t = 10 s.
Figure 4
Figure 4
3D Printing Experiments concerning the CP of Epoxysilicones upon irradiation with a Laser Diode (@405 nm): Characterization of the thick 3D generated patterns by numerical optical microscopy: (A) Coumarin 2/IOD (0.04%/0.8% w/w) (thickness = 1800 μm); (B) Coumarin 3/IOD (0.018%/0.36% w/w) (thickness = 1320 μm) and (C) Coumarin 7/IOD (0.05%/1% w/w) (thickness = 2200 μm); respectively.
Scheme 4
Scheme 4
Chemical Structures of the Commercial Coumarins used in this Work.
Scheme 5
Scheme 5
Chemical Structures of the Commercial Photoinitiators (IOD or SC939, CPTX and DBA) and Monomer (EPOX-Si200) used in this Study.
See this image and copyright information in PMC

References

    1. Steindl J., Svirkova A., Marchetti-Deschmann M., Moszner N., Gorsche C. Light-Triggered Radical Silane-Ene Chemistry Using a Monosubstituted Bis(Trimethylsilyl)Silane. Macromol. Chem. Phys. 2017;218:1600563. doi: 10.1002/macp.201600563. - DOI
    1. Nguyen L.H., Gu M. Decomposition Kinetics, Life Estimation, and Dielectric Study of an Acrylate Based Photopolymer for Microfabrication and Photonic Applications. Macromol. Chem. Phys. 2005;206:1659–1664. doi: 10.1002/macp.200500136. - DOI
    1. Tang C., Liu W. Synthesis of Cationic UV-Curable Methacrylate Copolymers and Properties of the Cured Films of Their Composites with Alicyclic Epoxy Resin. J. Appl. Polym. 2012;123:1724–1731. doi: 10.1002/app.34637. - DOI
    1. Balakrishnan P.S., Murugavel S.C. Spectral, Thermal, and Photoreactivity Studies on Epoxy Resin Containing Benzylidene Units in the Main Chain. J. Appl. Polym. 2009;111:2340–2344. doi: 10.1002/app.29200. - DOI
    1. Crivello J.V., Ortiz R.A. Design and Synthesis of Highly Reactive Photopolymerizable Epoxy Monomers. J. Polym. Sci. Part. A: Pol. Chem. 2001;39:2385–2395. doi: 10.1002/pola.1215. - DOI

LinkOut - more resources