Research on solvent-free acrylic pressure-sensitive adhesives (PSAs) has tremendously grown over the last few decades due to the stringent regulations to control volatile organic compound emissions. They are mostly prepared in the presence of photoinitiators using high-energy UV light that causes several issues such as those associated with radiation safety. Herein, for the first time, solvent-free acrylic PSAs were prepared through visible-light-driven photocatalytic free radical polymerization. Importantly, we found that the use of N-vinyl-based monomers noticeably enhances the rate and conversion of polymerizations, thereby eliminating the need for additives (e.g. α-haloester and sacrificial electron donor) that are usually required for photoredox-mediated free radical polymerization, but concurrently needs an additional purification process to remove residues. Combined experiments and quantum chemical calculations suggest that N-vinyl-based monomers facilitate electron transfer between monomers and photocatalysts, which is responsible for the enhanced rate and converison of polymerization. Viscoelasticity, mechanical strength and adhesion performance of acrylic PSAs were well adjusted in a broad range by controlling the monomer composition, suggesting that our new method would replace the existing photoinitiated free radical polymerization.

中文翻译：

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通过无添加剂的可见光驱动的光催化自由基聚合合成无溶剂丙烯酸压敏胶

由于控制挥发性有机化合物排放的严格规定，无溶剂丙烯酸压敏胶粘剂（PSA）的研究在过去几十年中得到了极大的发展。它们大多是在光引发剂存在下使用高能紫外光制备的，引起了一些问题，例如与辐射安全相关的问题。本文中，首次通过可见光驱动的光催化自由基聚合制备了无溶剂丙烯酸PSA。重要的是，我们发现使用基于N-乙烯基的单体显着提高了聚合反应的速率和转化率，从而消除了对添加剂的需求（例如光氧化还原介导的自由基聚合通常需要使用α-卤代酸酯和牺牲电子给体），但同时需要额外的纯化工艺以去除残留物。组合实验和量子化学计算表明，基于N-乙烯基的单体可促进单体与光催化剂之间的电子转移，这是聚合速率提高和聚合反应的原因。通过控制单体组成，可以在很宽的范围内很好地调节丙烯酸PSA的粘弹性，机械强度和粘合性能，这表明我们的新方法将替代现有的光引发自由基聚合。