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对于从包装到医疗设备的广泛应用来说，学术界和工业界都非常感兴趣。理想情况下，聚合物在执行其功能时应该是高度稳定的，但在所需的条件下会迅速分解。目前可用的材料通常通过随机主干断裂进行降解，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。拟议的研究计划旨在开发一类聚合物，该聚合物通过端到端解聚机制响应于聚合物末端的刺激响应端帽的切割而特异性降解。新的端帽响应不同的刺激，如氧化或还原物质的浓度变化，热，光，甚至这些刺激的多种组合将被开发，增强我们对其降解行为的理解，并展示了调整这些聚合物用于各种应用的潜力。通过对这些端盖的精心设计，还可以制备由多个块组成的聚合物。新单体的掺入将使聚合物的性质得以调整，进一步进行化学衍生化，并引入新的功能，如药物掺入。

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.