Visible-Light Photoinitiation of (Meth)acrylate Polymerization with Autonomous Post-conversion.
Visible-Light Photoinitiation of (Meth)acrylate Polymerization with Autonomous Post-conversion.
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自主后转化可见光引发(甲基)丙烯酸酯聚合。
DOI：
10.1021/acs.macromol.1c00761
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发表时间：
2021-09-14
期刊：
影响因子：
5.5
通讯作者：
Musgrave, Charles B.
中科院分区：
文献类型：
--
作者：
Kim, Kangmin;Sinha, Jasmine;Stansbury, Jeffrey W.;Musgrave, Charles B.
由于反应性自由基的快速终止，在自由基光聚合（RPP）中，在辐射中断后转化率迅速达到平台，这限制了RPP在涉及非均匀光接入的应用中的更广泛使用，包括具有衰减的光透射或不规则表面的那些应用。基于我们最近报道的一种自由基暗固化光引发剂（DCPI），该光引发剂通过在合适的氧化剂存在下使光释放胺的潜在氧化还原引发在停止照射之后继续聚合，我们开发了一种新的DCPI，其吸收光谱延伸到可见光范围内。我们的设计过程涉及一系列候选分子的计算研究，包括取代基及其位置依赖的吸收特性，电子跃迁，光化学机制及其相关的能量学的系统研究。我们的量子化学计算确定了目标化合物5，7-二甲氧基-6-溴-3-芳酰基香豆素-DMPT/BPh 4，并预测它将通过在可见光照射下同时产生光自由基和光诱导释放有效的氧化还原还原剂来促进暗固化机制。然后合成这种还原性束缚的发色团，并用紫外-可见光谱进行光学表征，显示其在405 nm处的摩尔吸光系数为5710 M−1 cm−1，在455 nm处的摩尔吸光系数为50 M−1 cm−1。然后，我们证明了在通过用455 nm LED照射短暂活化贮存稳定的单组分体系（在20%转化率时停止）后，在25分钟内具有>35%额外转化率的广泛暗固化。相比之下，在该相同点处对对照制剂进行遮蔽照射导致转化立即停止，其在20%处达到稳定。我们确定了一个显着的引发剂效率为2.82，结果从额外的氧化还原生成的自由基与77%的光还原剂生成量子产率。这种新型可见光DCPI的上级光固化和暗固化效率的组合有望在RPP中开辟新的应用机会，特别是那些涉及高度光衰减的树脂、具有产生不均匀辐照度的不规则特征的表面以及在光活化步骤下游连续暗固化提高生产线效率的生产线。
Conversion plateaus rapidly in radical photopolymerizations (RPPs) following discontinuation of irradiation due to rapid termination of reactive radicals, which restricts the wider use of RPPs in applications that involve nonuniform light access including those with attenuated light transmission or irregular surfaces. Based on our recent report of a radical dark-curing photoinitiator (DCPI) that continues polymerization beyond the cessation of irradiation by enabling latent redox initiation with photo-released amine in the presence of a suitable oxidant, we developed a new DCPI with an absorption spectrum that extends well into the visible range. Our design process involved a series of computational investigations of candidate molecules, including a systematic study of substituents and their position-dependent effects on absorption characteristics, electronic transitions, and the photochemical mechanism and its associated energetics. Our quantum chemical computations identified the target compound 5,7-dimethoxy-6-bromo-3-aroylcoumarin-DMPT/BPh4 and predicted that it would facilitate the dark-curing mechanism by concurrent photo-radical generation and photo-induced release of an efficient redox reductant under visible irradiation. This reductant-tethered chromophore was then synthesized and optically characterized with UV–vis spectroscopy that revealed its strong visible-light absorption with a molar absorptivity of 5710 M−1 cm−1 at 405 nm and 50 M−1 cm−1 at 455 nm. We then demonstrated extensive dark-curing of >35% additional conversion over 25 min following brief activation of the shelf-stable one-part system by irradiation with a 455 nm LED that was ceased at 20% conversion. In contrast, shuttering irradiation of the control formulation at that same point resulted in immediate cessation of conversion, which plateaued at 20%. We determined a remarkable initiator efficiency of 2.82 that results from the additional redox-generated radicals with a 77% photo-reductant generation quantum yield. The combination of superior photo- and dark-curing efficiencies of this new visible DCPI is expected to open new application opportunities in RPP, especially those involving resins that are highly light attenuating, surfaces that possess irregular features that produce uneven irradiance, and production lines where continued dark-curing downstream of the light activation step enhances line efficiencies.
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影响因子：
3.4
作者：
HAMMOND, GS;BARTLETT, PD
通讯作者：
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