New Designs for Degradable Polymers

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Polymers, commonly referred to as plastics, have many important roles in our daily lives. In food packaging, they provide physical protection, as well as a barrier to air and water, while being lighter and cheaper than glass or metal. They are also increasingly used in electronics and medicine. Many traditional applications of plastics have relied on their high long-term stability. For example, it is desired that plastic packaging retains its structure and properties for months or years, while the plastic used in joint replacements should survive for decades in the human body. However, there are growing concerns about the impact of plastic pollution on humans and the environment. It is predicted that almost 12,000 metric tons of plastic will have accumulated in landfills and the environment by 2050. Furthermore, for many applications of polymers in therapeutics and regenerative medicine, it is desired that polymers break down, rather than accumulate in the body. Therefore, the interest in developing degradable polymers has been growing. For example, significant progress has been made in the preparation and application of polyesters and polysaccharides. However, these polymers degrade gradually in many different environments, sometimes more slowly or more rapidly than desired, which hinders their widespread application. To gain a new level of control over when and where polymers degrade, my research team has been developing a new class of degradable polymers termed "self-immolative polymers" (SIPs). These polymers are designed to be stable during their use, but then to degrade (depolymerize) rapidly when triggered by a stimulus such as light, heat, mild acid, or other specific chemicals. They are chemically assembled such that a single stimulus event is sufficient to degrade an entire polymer chain. In addition, the stimulus to which they respond can be easily changed by switching a single capping molecule at the end of the polymer. So far, the number of SIPs and accessible properties is very limited. In this context, the objectives of the proposed research program are to: 1)Develop new SIP backbones, greatly expanding the array of accessible properties and applications. 2)Prepare and study new SIP architectures. Polymer chain shape often determines properties, but this aspect has been investigated very little for SIPs. We will explore this frontier. 3)Explore SIP surface coatings, demonstrating the potential for SIPs to address key practical challenges, including the development of antibacterial surfaces and reversible adhesives. The long-term vision for my research program is to develop a polymer chemistry "toolbox" that will enable excellent control over polymer degradation, eventually allowing degradable polymers to replace conventional polymers in many applications. These tools will also provide new properties and functions for applications in medicine and beyond.