CAS: Self-amplifying depolymerizable polymers

在化学部大分子、超分子和纳米化学项目的资助下，弗吉尼亚理工大学的John B. Matson教授正在构建基于聚（硫脲）和聚（烯烃砜）的合成聚合物，这些聚合物在应用于具有反应性和生物活性的气体中时会分解（解聚）。这两类聚合物都广泛用于各种工业应用，包括泡沫，粘合剂，建筑绝缘，甚至微电路制造。在这项研究中，高分子量聚硫脲是由使用计算模型设计的构建块制备的。然后发生化学反应，将这些聚合物解聚成硫化氢，这是一种存在于人体所有器官和系统中的重要生物气体。小剂量的硫化氢可以起到平滑肌松弛剂和血管舒张剂的作用，在大脑中也很活跃，可以增强某些受体的反应，促进长期记忆的形成。在一种相关的方法中，一种聚合技术被开发出来，以制备定义明确的聚（烯烃砜），这些聚（烯烃砜）能够解聚回最初由二氧化硫和小的不饱和烃组成的化合物。与该项目相关的化学方法与塑料回收的持续环境问题有关，其结果有可能推动可降解聚合物领域的发展。本研究的教育目标是提高阿巴拉契亚地区中小学生对高分子科学的热情。外展工作与弗吉尼亚理工大学青年体验科学（YES）暑期项目相结合，该项目侧重于与塑料相关的实践活动。本研究的重点是可解聚聚合物，也称为自焚聚合物，在特定刺激下进行端到端解聚。合成方法被开发出来以一种可控的方式制造可解聚的聚合物，这些聚合物可以解压缩产生既具有活性又具有生物活性的气体，在某些情况下可以进一步解聚（自扩增）。重点是两种类型的聚合物——聚（硫脲），它通过解聚生成羰基硫醚或硫化氢，聚（烯烃砜），它解聚生成二氧化硫和α -烯烃。在聚（硫脲）的情况下，计算方法被用来预测单体具有强大的聚合驱动力，并进行聚合，使所得到的聚合物在链端含有各种官能团，以触发解聚。此外，采用可逆失活自由基聚合的方法，从α -烯烃和二氧化硫开始，制备了性能良好的聚烯烃砜。聚合物胶束也被开发，包含特定的端基，使解聚事件的自扩增。其结果是，只有一个单一的触发事件在一个聚合物链端导致整个胶束核心的解聚。本研究具有推动可降解聚合物或具有可降解嵌段共聚物的发展的潜力。在解聚过程中产生的信号气体如二氧化硫和硫化氢也与许多生物应用有关。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 funding from the Macromolecular, Supramolecular and Nanochemistry Program of the Chemistry Division, Professor John B. Matson of Virginia Tech is building synthetic polymers based on poly(thiourethanes) and poly(olefin sulfones) that fall apart (depolymerize) upon application on cue into gases that are both reactive and bioactive. Both classes of polymers are used in a wide variety of industrial applications, including foams, adhesives, building insulation, and even microcircuit fabrication. In this research, high molecular weight poly(thiourethanes) are prepared from building blocks designed using computational modelling. Chemical reactions are then developed to depolymerize these polymers into hydrogen sulfide, a vital biological gas present in all organs and systems in a human body. Hydrogen sulfide, in small doses, acts as a relaxant of smooth muscle and as a vasodilator and is also active in the brain, where it increases the response of some receptors and facilitates long term memory formation. In a related approach, a polymerization technique is developed to prepare well-defined poly(olefin sulfones) that are capable of depolymerizing back into the compounds that they are originally made from sulfur dioxide and small unsaturated hydrocarbons. Chemical approaches associated with this project are of relevance to the ongoing environmental problem of plastic recycling, and the results have the potential to advance the field of degradable polymers. The educational goals of this research focus on increasing enthusiasm for polymer science in elementary and middle school children in Appalachia. Outreach efforts are integrated with the Virginia Tech Youth Experiencing Science (YES) summer program that focuses on hands-on activities related to plastics.This research focuses on depolymerizable polymers, also called self-immolative polymers, that undergo end-to-end depolymerization in response to a specific stimulus. Synthetic methods are developed to make depolymerizable polymers in a controlled manner, which can unzip to generate gases that are both reactive and bioactive, in some cases enabling further depolymerization (self-amplification). A strong emphasis is placed on two types of polymers—poly(thiourethanes), which undergo depolymerization to generate carbonyl sulfide or hydrogen sulfide, and poly(olefin sulfones), which depolymerize to generate sulfur dioxide and alpha-olefins. In the case of poly(thiourethanes), computational methods are used to predict monomers with strong driving forces for polymerization, and their polymerization is carried out such that the resulting polymers contain various functional groups on the chain-end to trigger depolymerization. In addition, well-defined poly(olefin sulfones) are prepared using reversible-deactivation radical polymerization methods starting from alpha-olefins and sulfur dioxide. Polymer micelles are also developed that contain specific end groups that enable self-amplification of the depolymerization event. As a result, only a single triggering event on one polymer chain-end leads to depolymerization of an entire micelle core. This research has the potential to advance the development of degradable polymers or block copolymers with a degradable block. Generation of signaling gases such as sulfur dioxide and hydrogen sulfide during the depolymerization process is also of relevance to many biological applications.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.