Effect of Polymer Network Architecture, Enhancing Soft Materials Using Orthogonal Dynamic Bonds in an Interpenetrating Network

Abstract

Doubly dynamic polymer networks were synthesized with two distinct exchangeable cross-linkers. The first linker is highly dynamic and rapidly exchanging hydrogen bonded 2-ureido-4­[1H]-pyrimidinone (UPy) and the second is a thermoresponsive furan-maleimide Diels–Alder adduct (FMI). Two network architectures were considered: an interpenetrating network (IPN) where one network is cross-linked with the UPy linker and the other is cross-linked with the FMI linker, and a single network (SN) where both the UPy and FMI linkers are in the same single network. Remarkably, the IPNs were superior to the SNs with the same composition of the UPy and FMI cross-linkers when comparing peak stress, strain at break, fracture toughness, malleability, and self-healing. Both materials studied were stable and creep resistant under ambient conditions.

Computational Investigation of the Effect of Network Architecture on Mechanical Properties of Dynamically Cross‐Linked Polymer Materials

“…In this model, red–red connection will represent a covalent cross‐linking and (dark)green–(dark)green connections represent noncovalent cross‐linkers. Figure c demonstrates the difference in cross‐linker configuration for interpenetrating (IPN) and single (SN) networks, modeling systems discussed in previous experimental work . IPN includes chains that are either only connected through covalent cross‐linkers (red spheres) or only connected through noncovalent cross‐linkers (dark green spheres).…”

“…However, they are typically incapable of self‐healing until substantial external stimulus is applied in the form of heat, pH swing, or light . This creates a fundamental trade‐off between dynamic character and stability against creep that cannot be resolved only with one type of dynamic linkage . Using both types of cross‐linkers in polymer networks provides a reasonable solution to address this challenge with a mechanically strong and dynamically responsive self‐healing system .…”

“…This creates a fundamental trade‐off between dynamic character and stability against creep that cannot be resolved only with one type of dynamic linkage . Using both types of cross‐linkers in polymer networks provides a reasonable solution to address this challenge with a mechanically strong and dynamically responsive self‐healing system . Over the past few years, different groups have established experimental procedures to achieve this goal .…”

“…Using both types of cross‐linkers in polymer networks provides a reasonable solution to address this challenge with a mechanically strong and dynamically responsive self‐healing system . Over the past few years, different groups have established experimental procedures to achieve this goal . As a result, single networks (SN) and interpenetrating networks (IPN) have emerged as two important types of polymer networks that take advantage of combining noncovalent and covalent cross‐linkers.…”

“…Over the past few years, different groups have established experimental procedures to achieve this goal . As a result, single networks (SN) and interpenetrating networks (IPN) have emerged as two important types of polymer networks that take advantage of combining noncovalent and covalent cross‐linkers. Previous work in the literature has demonstrated significant progress in synthesizing SN and IPN configurations and measuring few different chemical and physical properties of these networks such as elastic properties.…”