Dynamic Contributions to the Bulk Mechanical Properties of Self-Assembled Polymer Networks with Reconfigurable Bonds

Abstract

Soft materials that contain dynamic and reversible bonds exhibit unique properties including unusual extensibility, reversible elasticity, and self-healing capabilities, for example. Catechol motifs are of particular interest owing to their ability to form many kinds of reversible bonds; however, there are few reports on the role of hydrogen bonds between catechols. Here, physically crosslinked self-assembled networks composed of catechol-functionalized ABA triblock co-polymers are synthesized and characterized to elucidate the role of intermolecular bonding between catechol motifs on bulk mechanical properties. The Young's moduli of equilibrated networks range from 16 to 43 MPa. Furthermore, the concentration of intermolecular interaction is controlled indirectly by synthesizing polymers with prescribed catechol concentrations on each A block. Further, network dynamics are characterized by measuring the relaxation spectrum, and it is found that the network mean relaxation time is inversely related to catechol density. Finally, networks exhibit time-dependent recovery after uniaxial strain. These findings establish important relationships between molecular design, network composition, and macroscopic mechanical properties of model soft matter networks with dynamic intermolecular bonds. Furthermore, this insight has the potential to guide the design of dissipative materials for use in applications ranging from consumer products to surgical materials.