CAREER: Development of Catalytic, Sulfur-Free Chain Transfer Agents to Improve Mechanical and Material Performance of Crosslinked Photopolymers

在化学部（CHE）的化学催化（CAT）和大分子，超分子和纳米化学（MSN）计划以及材料研究部（DMR）的聚合物计划的资助下，丹佛大学的布雷迪沃勒尔将开发一种催化，无硫链转移剂（CTA），用于有效地创建光聚合物。塑料的一个重要子集是光聚合物，或用光产生的交联材料。光聚合物构成了3D打印、牙科和生物材料中常用材料的聚合物组分，然而，只有有限的机械性能窗口可以很容易地从可用的化学原料中获得。在这里提出的工作中，Worrell博士和他的团队将创造催化剂，这些催化剂有可能显着改变光聚合物的机械性能，同时保持99%的化学成分相同。Worrell博士还将建立和运行夏季高中实习：丹佛大学的新实验主义者（SHINE @ DU）计划，旨在为当地代表性不足的高中生提供在化学生物化学系主持的真实世界的研究经验。作为CAREER奖项的一部分，将建立一个由本科生主导的在线期刊，详细介绍有机聚合物的可扩展、简单和廉价的制备方法。由光聚合产生的材料本身具有高度交联性，并且会受到显著的收缩应力，通常很脆，材料性能范围有限。已经研究和开发了各种类型的链转移剂（CTA）以降低光聚合物的交联密度。尽管CTA在操纵光聚合物的机械性能方面是成功的，但它们需要高负载（高达总制剂的20重量%）并且经常含有硫，硫是恶臭的并且可以产生不稳定的制剂。Worrell博士和他的研究团队正在开发一种催化的无硫CTA，可以以ppm的数量添加到现有的商业单体原料中，以产生类似于使用传统CTA制备的光聚合物，但负载量低10，000倍。 将探索大环钴（II）催化剂的几种类似物，以提高树脂的溶解度和各种配体将筛选在一个高通量的方式在寻找有效的催化剂：配体组合。这些催化CTA将在商业3D打印树脂和液晶弹性体中进行测试，以缩小和降低玻璃化转变温度，降低储能模量，并改变其他相关的机械性能。该奖项反映了NSF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 funding from the Chemical Catalysis (CAT) and Macromolecular, Supramolecular, and Nanochemistry (MSN) Programs of the Division of Chemistry (CHE), and the Polymer Program of Division of Materials Research (DMR), Brady Worrell of the University of Denver will develop a catalytic, sulfur-free chain transfer agent (CTA) for efficiently creating photopolymers. An important subset of plastics is photopolymer, or crosslinked materials created with light. Photopolymers make up the polymer component of materials commonly used in 3D printing, dentistry, and biomaterials, however, only a limited window of mechanical properties can easily be accessed from available chemical feedstocks. In the work proposed here, Dr. Worrell and his team will create catalysts that have the potential to significantly alter the mechanical properties of photopolymers while keeping 99% of the chemical composition the same. Dr. Worrell will also establish and run the Summer High school Internships: New Experimentalists at University of Denver (SHINE @ DU) program, which aims to offer local, under-represented high school students real-world research experiences hosted in the Department of Chemistry & Biochemistry. An undergraduate led online journal detailing scalable, simple, and inexpensive preparations of organic polymers is to be established as part of this CAREER award effort.The materials generated by photopolymerization are inherently highly crosslinked and suffer from significant shrinkage stress, are often brittle, and have a limited range of material properties. Various classes of chain transfer agents (CTAs) have been investigated and developed to reduce the crosslinking density of photopolymers. Although CTAs are successful in manipulating the mechanical properties of photopolymers, they are required in high loadings (up to 20 wt% of total formulation) and frequently contain sulfur which is malodorous and can create unstable formulations. Dr. Worrell and his research team are developing a catalytic, sulfur-free CTA that can be added in ppm quantities to existing commercial monomer feedstocks to create photopolymers similar to those prepared using traditional CTAs, but at 10,000x lower loadings. Several analogs of the macrocyclic cobalt(II) catalyst will be explored to improve resin solubility and various ligands will be screened in a high-throughput fashion in the search for potent catalyst:ligand combinations. These catalytic CTAs will be tested in commercial 3D printing resins and liquid crystal elastomers to narrow and reduce the glass transition temperature, reduce storage modulus, and alter other pertinent mechanical properties.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.