Polymers/plastics play a critical role in almost every aspect of our daily life. Generally, most plastics in everyday use are passive, that is, designed for a single purpose (e.g., food containers, plastic bags, or adhesives) and once used these plastics are thrown away and impact the environment. This project is focused on developing a class of adaptive polymers that have the ability to heal or change shape on demand. In addition, these materials have the ability to be reprocessed after use, and by controlling the temperature and time employed during reprocessing it is possible to tailor their physical properties (e.g., stiffness, elasticity, temperature response). The ability to precisely retool the material properties opens the door to targeting materials that can be easily and systematically changed by processing, which in turn expands the potential applications areas that they can be used for. The research is a mix of different disciplines within the polymer area, from chemistry to polymer processing and mechanical characterization. Importantly, this broad research approach provides students (at all levels) with wide-ranging educational experiences covering this swath of topics. Graduate students will participate in a two-year outreach training program to develop and refine their abilities to engage and effectively communicate with the general public. Using this training they will participate in a series of outreach events, including Junior Science Cafés, the No Small Matter Molecular Engineering Fair, as well as a number of programs aimed at outreach to students from local Chicago public schools. These outreach activities, in conjunction with additional integrated high-school and undergraduate research opportunities, are designed to increase the fraction of underrepresented minorities in science and engineering.
PART 2: TECHNICAL SUMMARY
Recent work by the Rowan group has shown that room temperature dynamic thia-Michael (tM) chemistry (based on benzalcyanoacetate/amide Michael acceptors) can be used to access mechanically robust polymer networks through a process coined dynamic reaction-induced phase separation (DRIPS). These phase separated dynamic materials exhibit properties such as healing, shape memory, and reversible adhesion. Furthermore, the exchange kinetics and thermodynamics of tM reactions can be systematically altered by the electronic nature of the tM acceptor, allowing an investigation of how the dynamic exchange properties impact both the phase-separated morphology and the overall materials properties of the network. The planned research investigates the manipulation of dynamic tM materials through annealing conditions, light exposure, and cross-reactivity with additional dynamic bonding systems. In addition, the phase separated morphology (and therefore mechanical properties) of these materials can be directly manipulated through thermal processing conditions (cooling rates, annealing steps, etc.). As such, the first goal of this work is aimed at developing fundamental structure / processing / morphology / property relationships in this class of adaptive materials. The second goal of this work is to develop photo-responsive dynamic tM bonds by taking advantage of the inherent E/Z isomerism of the benzalcyanoacetate/amide Michael acceptor structure, to give access to a new class of photo-activated dynamic materials. Finally, a new program will be initiated aimed at using a Systems Polymer Science approach (inspired by systems chemistry) to functional polymer design with the goal of accessing pluripotent polymers, namely polymer systems whose properties can be significantly altered upon exposure to chemical or environmental cues allowing them to be used in a wide variety of applications. To do this, the PI will investigate the potential of incorporating multiple communicating dynamic reaction cycles into polymer networks. .
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.
