Photoinduced SET to access olefin-acrylate copolymers
Photoinduced SET to access olefin-acrylate copolymers
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DOI：
10.1039/d1py01643a
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发表时间：
2022-01-13
影响因子：
4.6
通讯作者：
Sumerlin, Brent S.
中科院分区：
文献类型：
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作者：
Garrison, John B.;Hughes, Rhys W.;Sumerlin, Brent S.
非极性烯烃单体与活性乙烯基单体结合所产生的有利的材料性能导致了可行的共聚策略的开发取得了相当大的进展。然而，在自由基共聚过程中，两者的竞聚率不佳会导致低水平的烯烃掺入，当试图通过通常应用于烯烃的配位-插入途径并入许多极性乙烯基单体时，会产生大量有害的副反应。我们认为，设计一种活性单体，不仅适合于与极性乙烯基单体(如丙烯酸酯)的自由基共聚，而且能够进行聚合后修饰以揭示烯烃重复单元，将允许制备统计的烯烃-丙烯酸酯共聚物。在这里，我们报道了符合这些标准的单体，并介绍了一种基于单电子转移(SET)诱导的直接在聚合物主链上产生脱羧基的聚合后修饰策略。具体地说，从有机光催化剂(曙红Y)到含有氧化还原活性邻苯二甲酰亚胺酯单元的聚合物在绿光下会导致聚合物主干上产生活性碳中心自由基。我们利用这种方法通过在氢原子供体存在下进行脱羧基生成统计的烯烃-丙烯酸酯共聚物，从而使主链自由基被氢原子封顶，从而产生乙烯或丙烯重复单元。这种方法允许制备具有以前无法获得的共聚单体分布的共聚物，并展示了应用基于集合的转化来解决聚合物化学中的长期挑战的前景。
The advantageous material properties that arise from combining non-polar olefin monomers with activated vinyl monomers have led to considerable progress in the development of viable copolymerization strategies. However, unfavorable reactivity ratios during radical copolymerization of the two result in low levels of olefin incorporation, and an abundance of deleterious side reactions arise when attempting to incorporate many polar vinyl monomers via the coordination-insertion pathway typically applied to olefins. We reasoned that design of an activated monomer that is not only well-suited for radical copolymerization with polar vinyl monomers (e.g., acrylates) but is also capable of undergoing post-polymerization modification to unveil an olefin repeat unit would allow for the preparation of statistical olefin-acrylate copolymers. Herein, we report monomers fitting these criteria and introduce a post-polymerization modification strategy based on single-electron transfer (SET)-induced decarboxylative radical generation directly on the polymer backbone. Specifically, SET from an organic photocatalyst (eosin Y) to a polymer containing redox-active phthalimide ester units under green light leads to the generation of reactive carbon-centered radicals on the polymer backbone. We utilized this approach to generate statistical olefin-acrylate copolymers by performing the decarboxylation in the presence of a hydrogen atom donor such that the backbone radical is capped by a hydrogen atom to yield an ethylene or propylene repeat unit. This method allows for the preparation of copolymers with previously inaccessible comonomer distributions and demonstrates the promise of applying SET-based transformations to address long-standing challenges in polymer chemistry.