Limitations of Diels–Alder Dynamic Covalent Networks as Thermal Conductivity Switches

Abstract

Creating polymers that exhibit a switchable thermal conductivity requires a fundamental understanding of how polymer structure and inter- and intramolecular interactions influence thermal transport. To develop this fundamental understanding, we synthesize a series of precursor un-cross-linked statistical copolymers with varying mole fractions of furan functional groups via reversible-addition fragmentation chain transfer (RAFT) polymerization. These precursor polymers, containing the furan diene, were then cross-linked using a reversible Diels–Alder cycloaddition to form dynamic covalent networks of varying cross-link densities. Furthermore, two separate dienophile cross-linkers were used to investigate how the molecular weight and length of the cross-linker influence the mechanical and thermal properties of the network. Counter to some recent theoretical studies, we found that both the elastic modulus and thermal conductivity were largely unaffected by the extent of cross-linking and the structure of the cross-linker. For this system, the Diels–Alder reaction was also found to be slow in the solid state, further limiting its utility as a thermal conductivity switch.

Structurally Dynamic Gelatin-Based Hydrogels with Self-Healing, Shape Memory, and Cytocompatible Properties for 4D Printing

“…The dynamic feature of the hydrogels that were crosslinked by a reversible imine/DA and supramolecular H-bonding dual network was next studied. Because imine bonds can be broken down under acidic conditions and the DA bond is reversible at highly elevated temperatures, − the imine/DA network should collapse with either pH or temperature stimulus. However, single-parameter changes, for example, adjusting the solution acidity to pH = 1 or temperature to 130 °C, did not lead to the dissolution of the hydrogel DNG-3 , even after prolonged time intervals (Figure S7a,b).…”

Rapid synthesis of functional poly(ester amide)s through thiol–ene chemistry

“…Preparation of a PEA-based reversible cross-linked network Retro-Diels-Alder reactions between dienes and dienophiles are an efficient strategy for reversible cross-linked network formation. 50,51 To illustrate the potential applications of our modied PEAs, a PA-1E-based reversible network was prepared via a retro-Diels-Alder reaction. 1,6-Bis(maleimido)hexane (1,6-BMH, Fig.…”

Organically surface engineered mesoporous silica nanoparticles control the release of quercetin by pH stimuli

“…Synthesis of AmEA compound was conducted by modifying procedure reported by previous work 32 , 33 . Briefly, maleic anhydride (1.961 g, 0.019 mol) was crushed into fine powder.…”