Internal and external catalysis in boronic ester networks
Year: 2021
Type: preprint
Abstract: In dynamic materials, the reversible condensation between boronic acids and diols provides adaptability, self-healing ability, and responsiveness to small molecules and pH. Recent work has shown that the thermodynamics and kinetics of bond exchange determine the mechanical properties of dynamic polymer networks. However, prior studies have focused on how structural and environmental factors influence boronic acid–diol binding affinity, and design rules for tuning the kinetics of this dynamic bond are lacking. In this work, we investigate the effects of diol (or polyol) structure and salt additives on the rate of bond exchange, binding affinity, and the mechanical properties of the corresponding polymer networks. To better mimic the environment of polymer networks in our small-molecule model systems, we incorporated proximal amide groups, which are used to conjugate diols to polymers, and included salts commonly found in buffers. Using one-dimensional selective exchange spectroscopy (1D EXSY), we find that both proximal amides and buffering anions induce significant rate acceleration consistent with internal and external catalysis, respectively. This rate acceleration is reflected in the stress relaxation of gels formed using PEG modified with different alcohols, and in the presence of salts containing acetate or phosphate. These findings contribute to the fundamental understanding of the boronic ester dynamic bond and offer new molecular strategies to tune the macromolecular properties of dynamic materials.
Authors: Boyeong Kang, Julia Kalow
Institution: Northwestern University
Language: English
Subfield: Polymers and Plastics
Field: Materials Science
Domain: Physical Sciences
Open Access status: green
Funders: National Science Foundation, Northwestern University, National Institutes of Health, Materials Research Science and Engineering Center, Harvard University, International Institute for Nanotechnology, Northwestern University, National Institute of General Medical Sciences, Division of Materials Research, Division of Electrical, Communications and Cyber Systems, Division of Chemistry
Awards: CAREER: Photocontrolled Dynamic Covalent Crosslinkers for Light-Responsive Polymer Networks, G1169090945, G1276186940, G1329306526, Acquisition of a 500 MHz NMR Spectrometer for Chemical Research, G2137585358, Development of Photoreversible 4D Cell Culture Technologies, G2604586490, G336680401, G3454132534, G4285583887, G4289625387, G4433393426, MRSEC: Center for Multifunctional Materials, G4912152698, G5218300437, G5306386714, NNCI: Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource, G5986892838, G6386240557, G6671297155, G7304483037, G7570481651, G801469781, G8073314406, G8230932042
OpenAlex ID: W3214160903