CAS: Responsive Macromolecules by Wavelength Controlled Vinyl Ketone Photopolymerization and Photodegradation

在化学系大分子、超分子和纳米化学项目的支持下，迈阿密大学的Dominik Konkolewicz正在利用自由基光聚合技术制备定义明确、可光降解的乙烯基酮聚合物。聚乙烯酮是一类聚合物，不仅广泛用作包装材料和农用薄膜的成分，而且还作为功能塑料应用于成像、微加工和传感器等领域。这些聚合物的一个有趣的特点是，在紫外线照射下，它们可以降解成低分子量的碎片，使它们非常适合回收利用。本研究将重点研究各种乙烯酮自由基光聚合和光降解的化学机制。获得的机理见解将用于开发光控塑料，这种塑料在可见光下制备，在紫外线照射下降解。该项目的更广泛影响将涉及发展和实施吸引初高中学生的外展活动。通过美国化学会的高分子化学和高分子材料科学与工程部门，该项目将通过社区资源和推广大分子联盟（MACRO）以及网络研讨会开发教育资源，吸引高分子化学社区的成员。该项目还将为不同背景的研究生和本科生提供培训和指导。来自服务不足群体的本科生将通过与路易斯斯托克斯少数民族参与联盟（LSAMP）的接触进行招募和指导，特别侧重于通过第一年的研究经验项目为LSAMP学生的研究做准备。乙烯基酮是一种独特的光活性单体，导致聚合物具有独特的光响应特性。然而，乙烯基酮的充分潜力和广泛应用受到阻碍，部分原因是单体反应性和潜在的聚合机制的不完全了解。本研究将对乙烯酮光聚合和光降解过程中自由基的生成机理进行研究。所开发的方法可以为乙烯基酮在可逆加成-裂解链转移（RAFT）聚合中提供独特的机会，以获得不同的官能团。还将进行详细的机理研究，以解决乙烯基酮的原子转移自由基聚合（ATRP）的挑战，并进一步了解这些复杂单体的有效聚合途径。此外，利用这些对乙烯基酮聚合机理的了解，光化学聚合诱导的自组装（photoPISA）和光化学降解诱导的自组装修饰（photoDIMSA）将被用于促进和调节聚合物的自组装。DIMSA方法可以广泛地影响聚合物的自组装，以及刺激响应聚合物的靶向递送。如果这些研究成功，新的增材制造和3D打印技术可能会产生，通过正交光响应，一个波长的光合成先进的聚合物结构，而另一个波长的光通过在选定的区域进行聚合后降解来增加复杂性。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

With the support of the Macromolecular, Supramolecular and Nanochemistry program in the Division of Chemistry, Dominik Konkolewicz of Miami University is employing radical photopolymerization to prepare well-defined and photodegradable polymers made of vinyl ketones. Polyvinyl ketones are a class of polymers that are widely used not only as components for packaging materials and agricultural films, but also as functional plastics in applications such as imaging, microfabrication and sensors. An interesting feature of these polymers is that they can be degraded to their low-molecular weight fragment upon exposure to UV irradiation, making them ideally suitable for recycling. This research will focus on investigating chemical mechanisms of radical photopolymerization and photodegradation of a diverse range of vinyl ketones. The gained mechanistic insights will then be used to develop photo-gated plastics that are prepared under visible light and degrade under ultraviolet irradiation. Broader impacts from the project will involve the development and implementation of outreach activities that engage middle and high school students. Through the polymer chemistry and polymer materials science and engineering divisions of the American Chemical Society, the project will engage members of the polymer chemistry community by developing educational resources through the macromolecular alliance for community resources and outreach (MACRO), as well as webinars. The project will also provide training and mentoring of graduate and undergraduate students of diverse backgrounds. Undergraduate students from underserved groups will be recruited and mentored through engagement with the Louis Stokes Alliance for Minority Participation (LSAMP), with a specific focus on preparing LSAMP students for research through first year research experience project.Vinyl ketones are unique photoactive monomers leading to polymers that have distinct photo-responsive properties. However, the full potential and broad use of vinyl ketones has been hindered in part due to incomplete understanding of monomer reactivity and underlying polymerization mechanisms. This research will study the mechanism of radical generation in vinyl ketone photopolymerization and photodegradation. The developed methodology could offer unique opportunities for vinyl ketones in reversible addition–fragmentation chain transfer (RAFT) polymerization to enable access to diverse functional groups. Detailed mechanistic studies will also be performed to address challenges in atom transfer radical polymerization (ATRP) of vinyl ketones and further understand pathways toward efficient polymerization of these complex monomers. Furthermore, using these mechanistic insights into the polymerization of vinyl ketones, photochemical polymerization induced self-assembly (photoPISA) and photochemical degradation induced modifications of self-assembly (photoDIMSA) will be performed to promote and modulate the self-assembly of polymers. The DIMSA approach could impact the polymer self-assembly broadly, as well as targeted delivery in stimulus responsive polymers. If these studies are successful, new additive manufacturing and 3D printing technologies could result, enabled by orthogonal light responsiveness, with one wavelength of light synthesizing advanced polymeric structures, and the other wavelength adding complexity by post-polymerization degradation on selected regions.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.