Photoinitiated Polymerization Techniques and Applications

Photoinitiated polymerization harnesses light energy to generate reactive species that trigger chain‐growth or step‐growth polymer formation under mild conditions. Central to this approach are photoinitiators and photosensitisers that absorb photons and either cleave to form radicals or transfer energy/electrons to co-initiators. Techniques span ultraviolet, visible and near-infrared activation, with recent advances extending responsiveness into the visible and NIR regions for enhanced safety and deeper penetration. Transition metal complexes and semiconductor nanocrystals are increasingly employed to improve absorption spectra, redox activity and initiation efficiency. Applications cover coatings, adhesives, optoelectronic encapsulation, stereolithography and biomedical hydrogels, offering spatial and temporal control, rapid cure rates and energy savings. Ongoing challenges include tailoring absorption to specific light sources, minimising toxicity and achieving uniform cure in thick or filled systems. Integration with 3D printing and foldable electronics underscores the global significance of photoinitiated polymerisation for sustainable manufacturing and advanced material designs.

Research from Nature Portfolio

Recent studies have introduced a visible-light curing system for the rapid production of UV-blocking optically clear adhesives, addressing the challenge of curing in the presence of UV absorbers. By optimising photocatalyst selection and co-initiator design, curing speeds were increased by an order of magnitude while preserving transparency and flexibility, enabling enhanced protection for foldable displays and other light-sensitive devices under mild illumination conditions.

An alternative strategy has centred on near-infrared activation, in which upconversion nanoparticles bearing oxime-ester coumarin functionalities generate radicals under NIR irradiation through energy transfer and radical cleavage. This “dandelion-like” mechanism yields efficient initiation of free-radical and thiol–ene polymerisations under low-power NIR lasers, reducing thermal side-effects and opening pathways for deep-cure applications in biological and structural contexts.

Photoinitiated Polymerization Techniques and Applications publication trend

The graph below shows the total number of articles in photoinitiated polymerization techniques and applications across all publications each year (not limited to Nature Index journals).

Technical terms

Photoinitiator: A molecule or nanomaterial that absorbs light and generates reactive species to start polymerization.

Photosensitiser: A compound that transfers energy or electrons to a photoinitiator upon light absorption, extending the activation wavelength range.

Free radical polymerisation: A chain-growth process in which monomer units are linked by radicals generated from photoinitiators.

Thiol–ene polymerisation: A step-growth reaction between thiol and alkene groups mediated by radicals, known for rapid kinetics and uniform networks.

Upconversion nanoparticle: A nanocrystal that converts low-energy photons into higher-energy emissions, enabling activation of photoinitiators with near-infrared light.

Quantum photoinitiator: A semiconductor nanocrystal that initiates polymerisation by electronic excitation and charge transfer under illumination.

References

1. Recent Advances of Transition Metal Complexes for Photopolymerization and 3D Printing under Visible Light. Advanced Functional Materials (2023).
2. Ultraviolet light blocking optically clear adhesives for foldable displays via highly efficient visible-light curing. Nature Communications (2024).
3. High Photoinitiating Efficiency of Benzothioxanthene‐Based Oxime Esters in Photopolymerization via Photocleavage and/or Single Electron Transfer under Visible Light and Sunlight. Angewandte Chemie International Edition (2024).
4. ZnO Quantum Photoinitiators as an All-in-One Solution for Multifunctional Photopolymer Nanocomposites. ACS Nano (2023).
5. Highly efficient dandelion-like near-infrared light photoinitiator for free radical and thiol-ene photopolymerizations. Nature Communications (2019).