Under natural light, lignin can produce a small amount of free radicals, resulting in yellowing of lignin-related products. However, the activity of these free radicals is very low, so that few studies on exploring the application potential of lignin as photoinitiator (PI) in photopolymerization have been reported. In this study, based on dealkaline lignin (DAL), two alkylated DAL (DAL-11ene and DAL-12ane) were synthesized through facile one-step esterification reactions between DAL and undecanoyl chloride or dodecanoyl chloride. The photoinitiation properties of DAL, DAL-11ene, and DAL-12ane were investigated by real-time FTIR spectroscopy and NIR-photorheology using 1,6-hexanediol diacrylate as a monomer. The formation of reactive species was elucidated by laser flash photolysis and electron spin resonance. The results indicated that DAL itself showed a certain photoinitiating ability, especially when it was combined with an amine co-initiator, while both DAL-11ene and DAL-12ane presented much higher photoinitiating efficiencies compared with DAL. Moreover, DAL-11ene containing a polymerizable group could be bonded into the network of final polymer products, which can increase their biosafety. 3D structures of polyacrylates were fabricated successfully using DAL-11ene and DAL-12ane as PIs through digital light processing 3D printing upon 405 nm exposure, indicating their large potentials in photopolymerization.

中文翻译：

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改性脱碱碱木质素作为可见光大分子光引发剂用于3D打印的研究

在自然光下，木质素会产生少量自由基，导致木质素相关产品泛黄。然而，这些自由基的活性非常低，因此，很少有研究探索木质素作为光引发剂（PI）在光聚合中的应用潜力的研究。在这项研究中，基于脱碱木素（DAL），通过DAL与十一烷酰氯或十二烷酰氯之间的简单一步酯化反应，合成了两个烷基化DAL（DAL-11ene和DAL-12ane）。使用1,6-己二醇二丙烯酸酯作为单体，通过实时FTIR光谱和NIR光流变学研究了DAL，DAL-11ene和DAL-12ane的光引发性能。通过激光闪光光解和电子自旋共振阐明了反应性物质的形成。结果表明，DAL本身显示出一定的光引发能力，特别是与胺共引发剂结合使用时，而DAL-11ene和DAL-12ane均比DAL表现出更高的光引发效率。此外，含有可聚合基团的DAL-11ene可以键合到最终聚合物产品的网络中，从而可以提高其生物安全性。通过在405 nm曝光下进行数字光处理3D打印，使用DAL-11ene和DAL-12ane作为PI成功地制造了聚丙烯酸酯的3D结构，这表明它们在光聚合方面具有巨大潜力。含有可聚合基团的DAL-11ene可以键合到最终聚合物产品的网络中，从而可以提高其生物安全性。通过在405 nm曝光下进行数字光处理3D打印，使用DAL-11ene和DAL-12ane作为PI成功地制造了聚丙烯酸酯的3D结构，这表明它们在光聚合方面具有巨大潜力。含有可聚合基团的DAL-11ene可以键合到最终聚合物产品的网络中，从而可以提高其生物安全性。通过在405 nm曝光下进行数字光处理3D打印，使用DAL-11ene和DAL-12ane作为PI成功地制造了聚丙烯酸酯的3D结构，这表明它们在光聚合方面具有巨大潜力。