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

在化学系(CHE)的化学催化(CAT)、大分子、超分子和纳米化学(MSN)计划以及材料研究(DMR)的聚合物计划的资助下，丹佛大学的Brady Worrell将开发一种催化的、无硫的链转移剂(CTA)，用于高效地生成光聚合物。塑料的一个重要子集是光致聚合物，即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成分，然而，从现有的化学原料中可以很容易地获得有限的机械性能窗口。在这里提出的工作中，沃雷尔博士和他的团队将创造出催化剂，这种催化剂有可能显著改变光聚合物的机械性能，同时保持99%的化学成分不变。沃瑞尔博士还将建立并运营丹佛大学暑期高中实习生：新实验者计划(SINE@DU)，该计划旨在为当地代表不足的高中生提供由化学与生物化学系主持的真实研究体验。作为这项职业奖励工作的一部分，将建立一个本科生领导的在线期刊，详细介绍可扩展的、简单的和廉价的有机聚合物制剂。光聚合产生的材料固有地高度交联，遭受显著的收缩压力，通常是脆性的，并且材料性能范围有限。为了降低光聚合物的交联密度，人们研究和开发了各种链转移剂(CTA)。尽管CTA成功地控制了光致聚合物的机械性能，但它们需要在高负荷(高达总配方的20wt%)下使用，而且经常含有恶臭的硫，可能会产生不稳定的配方。Worrell博士和他的研究团队正在开发一种催化的、无硫的CTA，这种CTA可以以百万分之几的数量添加到现有的商业单体原料中，以创建与使用传统CTA制备的光聚合物类似的光聚合物，但负载量要低10000倍。将探索几种类似的大环钴(II)催化剂以改善树脂的溶解性，并将以高通量的方式筛选各种配体以寻找有效的催化剂：配体组合。这些催化CTA将在商用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，降低存储模数，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智力优势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.