Oxygen-tolerant green-light photopolymerizations with type I boron-alkylated BODIPYs: The power of a methylene

IF 19.1 1区化学 Q1 CHEMISTRY, MULTIDISCIPLINARY

Chem Pub Date : 2026-10-08 Epub Date: 2026-04-23 DOI:10.1016/j.chempr.2026.103043

Hyeong Seok Kim, Nirvana T. Almada, Elizabeth A. Recker, Seth R. Allen, Jaechul Ju, Connor J. O’Dea, Benjamin S. Saada, Madison G. Handojo, Kathleen N. Halwachs, Adrianne M. Rosales, Sean T. Roberts, Zachariah A. Page

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Page","doi":"10.1016/j.chempr.2026.103043","DOIUrl":null,"url":null,"abstract":"<div><ul><li><span>•</span><span><div>Oxygen-tolerant type-I photoinitiators activated by low-intensity green LEDs</div></span></li><li><span>•</span><span><div>Ethyl substitution yields 10× shorter inhibition times and ∼2× faster polymerizations</div></span></li><li><span>•</span><span><div>Spectroscopy confirms enhanced efficiency and selectivity for ethyl radical formation</div></span></li><li><span>•</span><span><div>Proof-of-concept ambient 3D printing with 2.5 s exposures at 3 mW cm<sup>−2</sup> intensity</div></span></li></ul></div><div>Type I photoinitiators generate radicals through light-induced homolytic bond cleavage, which has enabled photopolymerization processes used across the coatings, microelectronics, and 3D printing industries. However, most rely on ultraviolet (UV) light, which limits safety, reaction depth, and compatibility with sensitive materials. Visible-light systems offer milder activation and deeper light penetration but remain constrained by a narrow chemical scope and oxygen inhibition. To address these challenges, recent designs, such as acylgermanes and silyl ketones, have extended absorption to blue light. Building on this foundation, this work establishes boron-alkylated BODIPYs as a new class of oxygen-tolerant, visible-light type I photoinitiators operating efficiently under green light. Exchanging methyl substitution at boron for ethyl groups was found to dramatically lower the B–C bond dissociation energy, accelerate photolysis, and mitigate oxygen quenching, enabling rapid polymerization and open-air 3D printing of commercial acrylics. The modular BODIPY framework allows for the rational tuning of excited-state dynamics and photolysis efficiency through systematic boron substitution. 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引用次数: 0

Abstract

•
Oxygen-tolerant type-I photoinitiators activated by low-intensity green LEDs
•
Ethyl substitution yields 10× shorter inhibition times and ∼2× faster polymerizations
•
Spectroscopy confirms enhanced efficiency and selectivity for ethyl radical formation
•
Proof-of-concept ambient 3D printing with 2.5 s exposures at 3 mW cm⁻² intensity

Type I photoinitiators generate radicals through light-induced homolytic bond cleavage, which has enabled photopolymerization processes used across the coatings, microelectronics, and 3D printing industries. However, most rely on ultraviolet (UV) light, which limits safety, reaction depth, and compatibility with sensitive materials. Visible-light systems offer milder activation and deeper light penetration but remain constrained by a narrow chemical scope and oxygen inhibition. To address these challenges, recent designs, such as acylgermanes and silyl ketones, have extended absorption to blue light. Building on this foundation, this work establishes boron-alkylated BODIPYs as a new class of oxygen-tolerant, visible-light type I photoinitiators operating efficiently under green light. Exchanging methyl substitution at boron for ethyl groups was found to dramatically lower the B–C bond dissociation energy, accelerate photolysis, and mitigate oxygen quenching, enabling rapid polymerization and open-air 3D printing of commercial acrylics. The modular BODIPY framework allows for the rational tuning of excited-state dynamics and photolysis efficiency through systematic boron substitution. Looking forward, extending these design rules could yield more efficient, longer-wavelength, and biocompatible initiators for additive manufacturing, dental curing, and tissue engineering, representing a step toward safer and more energy-conscious light-driven technologies.

Conventional type I photoinitiators require high-energy ultraviolet (UV) light to generate radicals, whereas most visible-light systems rely on slower, oxygen-sensitive type II photosensitization pathways. We report boron-alkylated boron-dipyrromethenes (BODIPYs) as type I photoinitiators that operate efficiently under green-light-emitting diodes (LEDs) and ambient conditions. Replacing methyl with ethyl at the boron site accelerates photolysis, lowers the B–C bond dissociation energy, and suppresses oxygen sensitization. Consequently, the ethyl derivative doubles the polymerization rate and decreases oxygen inhibition times by over an order of magnitude. Relative to Ivocerin, a leading blue-light type I photoinitiator, the BODIPY system achieves a higher external quantum yield due to stronger absorption. Owing to these performance enhancements, the ethyl derivative enables rapid, ambient, green-light digital light processing (DLP) 3D printing of commercial acrylate resins, achieving 2.5 s exposures per 50 μm layer at 3 mW cm⁻². This oxygen-tolerant platform provides a practical, mild route for photocurable technologies.

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查看原文本刊更多论文

I型硼烷基化体dipys的耐氧绿光聚合：亚甲基的作用。

传统的I型光引发剂需要高能紫外线来产生自由基，而大多数可见光系统依赖于较慢的、对氧敏感的II型光氧化还原途径。我们报道了硼烷基化BODIPYs作为可见光I型光引发剂，在绿色led和环境条件下有效地工作。乙基取代，相对于甲基，在硼位点加速光解，降低B-C键离解能，抑制氧敏化。因此，与甲基类似物相比，乙基衍生物的聚合速率加倍，氧抑制次数减少一个数量级以上。相对于Ivocerin®（一种领先的蓝光I型光引发剂），BODIPY系统由于吸收更强而实现了更高的外量子产率。作为概念验证，乙基衍生物实现了商用丙烯酸酯树脂的快速环境绿光DLP 3D打印，在3 mW cm-2下每50 μm层曝光2.5 s。这种耐氧平台为光固化技术提供了一条实用、可持续的途径。

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来源期刊

Chem Environmental Science-Environmental Chemistry

CiteScore

32.40

自引率

1.30%

发文量

281

期刊介绍： Chem, affiliated with Cell as its sister journal, serves as a platform for groundbreaking research and illustrates how fundamental inquiries in chemistry and its related fields can contribute to addressing future global challenges. It was established in 2016, and is currently edited by Robert Eagling.