The [2 + 2] photopolymerization of diolefinic monomers is an appealing approach for the construction of polymeric materials. Herein, we demonstrate that the establishment of an effective donor–acceptor conjugation by introducing electron-donating alkoxy groups at appropriate positions of the benzene ring could activate p-phenylenediacrylate (PDA), thus enabling the development of the first solution [2 + 2] photopolymerization of such monomers under the irradiation of visible light. Variation on the alkoxy groups and the ester parts could allow access to a series of linear cyclobutane-containing polymer products with high molecular weight (up to 140 kDa) and good solubility in common solvents. Further, temporal control and postpolymerization modification with preinstalled pendant C═C bonds via thiol–ene click reaction are also demonstrated with this [2 + 2] photopolymerization system.

中文翻译：

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可见光下非密闭环境中 [2 + 2] 光聚合合成线性含环丁烷聚合物

双烯烃单体的 [2 + 2] 光聚合是构建聚合物材料的一种有吸引力的方法。在此，我们证明通过在苯环的适当位置引入供电子烷氧基来建立有效的供体-受体共轭可以激活p-苯二丙烯酸酯 (PDA)，从而能够开发出此类单体在可见光照射下的第一种溶液 [2 + 2] 光聚合。烷氧基和酯部分的变化可以获得一系列具有高分子量（高达 140 kDa）和在普通溶剂中具有良好溶解性的线性含环丁烷聚合物产品。此外，该 [2 + 2] 光聚合系统还展示了通过硫醇-烯点击反应使用预先安装的悬垂 C=C 键进行时间控制和聚合后修饰。