New mechanisms for controlled polymer degradation and their incorporation into functional three-dimensional materials

在环境或人体中降解为小分子的聚合物在从包装到医疗器械的广泛应用中受到学术界和工业界的极大关注。理想情况下，聚合物在执行其功能时将是高度稳定的，但在所需条件下将迅速分解。目前可用的材料通常通过随机主链断裂进行降解，并在广泛的环境中逐渐降解，限制了我们触发和控制这种降解的能力。拟议的研究计划的目的是开发一类聚合物，降解特定的端到端的解聚机制，响应于从聚合物末端的刺激响应性端帽的裂解。新的封端响应不同的刺激，如在氧化或还原物种，热，光，甚至多种组合的浓度变化，这样的刺激将被开发，提高我们的理解，其降解行为，并展示了潜在的调整这些聚合物的各种应用。通过仔细设计这些封端，也将制备由多个嵌段组成的聚合物。新单体的引入将使得聚合物的性质能够被调整，进一步进行化学衍生化，并且引入新功能，例如药物引入。 这些新的可解聚分子的最终功能将通过将其掺入三维材料中来实现。嵌段共聚物将被纳入纳米尺寸的组件，包括胶束和囊泡，这将是探索其封装和释放货物的能力，如抗癌药物，治疗性核酸，和生长因子的组织工程在一个可控的方式。该聚合物还将用于制造组织工程细胞生长的多孔支架。简单地通过改变封端来改变聚合物响应的刺激的能力，将在我们制备和研究响应于不同刺激的广泛的新材料的能力方面提供优于当前聚合物的显著优势。此外，在单一刺激介导的事件后降解整个聚合物链的能力可以提供刺激的显著放大，使得材料性质的变化能够在低的细胞相容的刺激浓度下发生。总的来说，这项研究将使我们对刺激响应材料的理解取得变革性进展，同时为目标应用提供新的特性和功能。

Polymers that undergo degradation to small molecules in the environment or in the human body are of significant interest to both academia and industry for a wide range of applications from packaging to medical devices. Ideally, a polymer would be highly stable while performing its function, but would break down rapidly under the desired conditions. Currently available materials typically undergo degradation by random backbone scission and degrade gradually in a wide range of environments, limiting our ability to trigger and control this degradation. The proposed research program aims to develop a class of polymers that degrade specifically by an end-to-end depolymerization mechanism in response to the cleavage of a stimuli-responsive end-cap from the polymer terminus. New end-caps responsive to different stimuli such as changes in the concentrations of oxidizing or reducing species, heat, light and even multiple combinations of such stimuli will be developed, enhancing our understanding of their degradation behavior and demonstrating the potential to tune these polymers for a variety of applications. Through careful design of these end-caps, polymers composed of multiple blocks will also be prepared. The incorporation of new monomers will enable the properties of the polymers to be tuned, further chemical derivatization to be performed, and for new functions such as drug incorporation to be introduced. The ultimate functions of these new depolymerizable molecules will be realized through their incorporation into 3-dimensional materials. Block copolymers will be incorporated into nanometer-sized assemblies including micelles and vesicles, which will be explored for their ability to encapsulate and release cargo such as anti-cancer drugs, therapeutic nucleic acids, and growth factors for tissue engineering in a controlled manner. The polymers will also be used to fabricate porous scaffolds for the growth of cells for tissue engineering. The ability to change the stimuli to which the polymers respond, simply by changing the end-cap, will offer a significant advantage over the current polymers in terms of our ability to prepare and study a wide range of new materials responsive to different stimuli. Furthermore, the ability to degrade an entire polymer chain following a single stimulus-mediated event can provide a significant amplification of the stimulus, enabling changes in material properties to occur at low, cell-compatible stimulus concentrations. Overall, this research will enable transformative advancements in our understanding of stimuli-responsive materials while at the same time affording new properties and functions for the target applications.