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. 2025 Sep 10;12(12):nwaf381.
doi: 10.1093/nsr/nwaf381. eCollection 2025 Dec.

Photo-induced energy-transfer polymerization

Jian Liu  1 , Yaxiong Wei  2 , Liangwei Ma  1 , Xin Jin  1 , Siyu Sun  1 , Shuyao Zhou  3 , Xinsheng Xu  2 , He Tian  1 , Xiang Ma  1
Affiliations

Photo-induced energy-transfer polymerization

Jian Liu et al. Natl Sci Rev. .

Abstract

In conventional photo-induced polymerization strategies, the active species that initiate the reaction tend to be exogenous radical species. Inspired by photo-induced cycloaddition reactions, in this study, we investigated photo-induced polymerization from the perspective of energy-transfer processes. Utilizing low-energy, highly reactive triplet species of olefin molecules as energy acceptors, a polymerization strategy without the need for exogenous active components was developed. Triplet species from various sources were able to induce polymerization, demonstrating the excellent versatility of this strategy. The reaction mechanism was thoroughly investigated with controlled experiments and spectroscopic methods using thiochromanone as a template. It was clearly established that the key to polymerization is an active triplet species rather than a conventional radical species. As a result, the findings of this study stimulate further discussion on the role of monomers in photo-induced polymerization.

Keywords: photocatalyst; polymerization; triplet–triplet energy transfer.

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Figures

Figure 1.
Figure 1.
Process of photo-induced energy-transfer polymerization. Proposed mechanism of (a) TTET-induced cycloaddition reaction and (b) TTET-induced polymerization. (c, d) Various PCs mentioned in this article. UC, upconversion; SF, singlet fission; Cz, carbazole.
Figure 2.
Figure 2.
DFT results of photo-induced energy-transfer polymerization. (a) Scheme of photo-induced energy-transfer polymerization. (b) Energy gap between ground-state monomers, triplet-state monomers and polymer products in DFT calculations using different monomers.
Figure 3.
Figure 3.
Spectrum data and catalytic performance of METOs. (a) Structures of METO-1–4. (b) Molar absorption coefficients of METO-1–4. (c) ISC efficiency of METO-1–4. (d) TTET efficiency between METO-1–4 and MMA. (e) Transition absorption (TA) spectra of METO-3. (f) Kinetic curve @370 nm of METO-3 before and after the addition of MMA. (g) Kinetic curves of the polymerization catalysed by METO-1–4.
Figure 4.
Figure 4.
Experiments verifying the mechanism. (a) Scheme of TTET-induced photopolymerization. (b) Illustration of three different reaction conditions. (c) Polymerization rate profiles of METO-3 in three different oxygen environments. (d) Classical triplet-sensitized cycloaddition reaction. Reaction time = 6 h. (e) Conversion of METO-3 into METO-4 as a photocatalyst for the reaction in (d).
Figure 5.
Figure 5.
Catalytic performance of various photocatalysts with other acrylate monomers. PC loading = 500 ppm (relative to monomer), reaction time = 24 h, RT.
See this image and copyright information in PMC

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