LEAPS-MPS: Synthesis of Dynamic Thiolate-Mediated Bifunctional Silyl Ether Exchange Polymers and Composites

Davidson College, Davidson NC

Investigators

Abstract

In this project, funded by the MPS-LEAPS (Launching Early-Career Academic Pathways) Program and managed by the Broadening Participation Program in the Division of Chemistry (CHE-BP), Professor Bassil El-Zaatari and his students at Davidson College will perform studies focused on the synthesis and characterization of covalent adaptable polymer networks (CANs) and composites based on thiolate-mediated bifunctional silyl ether exchanges. The challenge to reprocess and recycle cross-linked polymer networks remains an ongoing obstacle within the polymer community. Developing and applying dynamic chemistries in polymer networks represents an important avenue of exploration to impart reprocessing capabilities to polymer networks that cannot otherwise be reprocessed. Professor El-Zaatari and his students will develop a thiolate mediated mechanism to catalyze dynamic bifunctional silyl ether exchanges and explore its utility in cross-linked polymer networks and composites. Their studies could improve the understanding of structure-reactivity-property relationships of dynamic thiolate mediated silicone-containing thermosets and could lead to developing high-performance reprocessable nanocomposite materials. The research goals are integrated with an education plan that includes mentoring students from underrepresented groups, plans to create leadership opportunities on campus for research students, and fostering relationships between faculty and undergraduate students from other Primarily Undergraduate Institutions who research polymers. This proposal offers a stepwise approach towards developing cross-linked elastomers with intrinsic silyl ether dynamic bond exchange chemistry. Through the proposed work, optimization of thiolate mediated bifunctional silyl ether exchanges will be developed and kinetic studies on both small molecule and macromolecular scales will be performed. The scope of thiolates and silyl ethers that can undergo a dynamic exchange will be investigated using various characterization techniques such as NMR and GC-MS. The kinetic and mechanistic insights of the thiolate mediated silyl ether exchange will be utilized to guide the synthesis of dynamic cross-linked polymers and composites. The thermomechanical properties of the synthesized networks will be evaluated through rheology, dynamic mechanical analysis, differential scanning calorimetry and thermal gravimetric analysis. Importantly, the reprocessing capabilities of the polymers and composites will be assessed via stress relaxation experiments and, on a bulk scale, through hot pressing and welding experiments. Overall, the research combines molecular and macromolecular interactions, polymer chemistry, and sustainability through developing dynamic silyl ether exchange thermosets. 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.