Electrochemically Controlling the Ring Size and Molecular Topology of Cyclic Polyesters
Abstract
This effort seeks to develop a highly regulated electrochemical methodology for enabling the synthesis of precision cyclic polyesters with high fidelity control over ring size and molecular topology. As cyclic polyesters demonstrate increased thermostabilities, lower hydrodynamic volumes and lower melt viscosities relative to their linear counterparts, the ability to achieve controlled synthesis of these materials has the potential to render access to materials that are currently underexplored, but are anticipated to have intriguing material properties. The PI has identified two specific aims to address the aforementioned objective: (1) develop highly regulated electrochemical methods for introduction of N-heterocyclic carbene (NHC) catalysts and modulate the zwitterionic ring-opening polymerization of lactones to render precision cyclic polyester materials and (2) identify synthetic routes to novel catenane (interlocked cyclic structures) polyester architectures as catalyzed by multi-dentate NHC catalysts. The PI s working hypothesis is that the active NHC catalyst can be reversibly released and recovered if the reaction is initiated by a pre-catalyst under suitable electrochemical conditions. A variety of pre-catalyst adducts will be prepared and characterized via ultraviolet-visible spectroscopy, multi-nuclear nuclear magnetic resonance, mass spectroscopy, and single crystal X-ray crystallography. A detailed electrochemical investigation will also be performed on these adducts to ascertain electrochemical redox potentials. To demonstrate reversible binding of the NHC ligands to the metal complexes, an in situ ultraviolet-visible spectroelectrochemical study will be performed. In parallel, theoretical calculations will also be performed to gain a better understanding of the mechanism of reversibility. Lessons learned from these studies/calculations will be used to optimize the reaction conditions for the subsequent polymerization studies. All synthesized polymers will be characterized via gel permeation chromatography, nuclear magnetic resonance spectroscopy, and infrared spectroscopy spectroscopy. Polymer morphology will be studied via electron microscopy techniques. Differential scanning calorimetry and thermogravimetric analysis will be employed for thermal analysis. In addition, dynamic mechanical analysis, viscometry, and rheometry will be used to characterize the polymers viscoelastic behavior.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jan 12, 2017
- Source ID
- W911NF1610197
Entities
People
- Kuppuswamy Arumugam
Organizations
- Army Contracting Command
- United States Army
- Wright State University