Kinetic and thermodynamic measurements for the facile property prediction of diels–alder‐conjugated material behavior

Abstract

The Diels–Alder (DA) reaction between maleimide and furan moieties possessing various substitutions was performed as a means for developing predictive capabilities for temperature and conversion‐dependent material properties in networks comprised of DA moieties. Using HNMR spectroscopy, the reactions of maleimide‐ and furan‐containing molecules further functionalized with carboxylic acids were monitored to ascertain the impact that substitutional changes had on the thermodynamic and kinetic behavior of the DA reaction. The reaction rate and equilibrium conversion of the furan and maleimide increased when the carboxylic acid functional group directly connected to the furan ring was moved from the two to the three position. When an aliphatic two‐carbon spacer was used, such that the π‐electrons of the carboxylic acid and furan were no longer conjugated, the reaction rate increased further. We also report the reactivity effect on the distance between the carboxylic acid functional group and the maleimide, which yielded little impact on the reaction rate but exhibited increased equilibrium conversion with increasing distance. Additionally, the impact on the kinetic and thermodynamic properties of coupling the carboxylic acid to another molecule, tert‐butyl glycine, was also determined. When the carboxylic acid was coupled to an amine, the DA reaction between the furan and maleimide was generally found to have similar kinetic and thermodynamic behavior as compared to their uncoupled, carboxylic acid equivalents. Thus, the characterized and tabulated kinetic and thermodynamic data presented herein enables the prediction of a broad set of temperature‐dependent chemical and material properties. Finally, we discuss practical limitations and nuances of the DA reaction, such as the potential for the maleimide to ring‐open in aqueous media via hydrolysis. © 2012 American Institute of Chemical Engineers AIChE J, 2012

Phosphonated furan-functionalized poly(ethylene oxide)s using orthogonal click chemistries: synthesis and Diels–Alder reactivity

“…The acceleration of the DA reaction in water solution is in accordance with previous studies involving non-polymeric cycloreactants 33,[35][36][37][38] and can been ascribed to enforced hydrophobic interactions between the cycloreactants and hydrogenbonding interactions between the dipolarophile and the solvent, both stabilizing the transition state. 37 The reactivity of the phosphonic acid homologue 6b showed a less pronounced water-induced acceleration as compared to that of 5b (run 3 vs. 4 & run 7 vs. 8, Table 2), probably due to the presence of the strong hydrophilic character of the phosphonic acid moiety near the diene, which restricts the stabilizing hydrophobic interactions with the dienophiles in the transition state.…”

Characterization and kinetic study of Diels-Alder reaction: Detailed study on N-phenylmaleimide and furan based benzoxazine with potential self-healing application

“…So far, the majority of the research was focused on the modified benzoxazines describing effects of maleimide or furan functionality on the mechanical properties of polymeric benzoxazines, while the use of Diels-Alder reaction in self-healing perspective has not yet been recognized [17][18][19][20][21][22]. Needless to say, numerous studies were performed to date dealing with the DA reaction based on maleimide and furan functionalities [6,16,[23][24][25][26][27][28]. Only a few examples in literature exist, where benzoxazines were used in DA reactions to form linear polymeric materials [29,30].…”

Harnessing entropy to direct the bonding/debonding of polymer systems based on reversible chemistry

“…However, we assert that tuning the entropy of a reversibly bonding system can have equally dramatic effects on the debonding temperature. Although a few publications 21,22 have either directly or indirectly noted the effects of polymer/monomer topology/backbone properties on reversibly debonding polymer systems, no one appears to have correctly isolated the entropic component to analyze its effects on debonding. Here, we propose that the inuence of entropy on polymer debonding can be well isolated and analyzed by changing the chain length of the monomeric linkers in a polymer while preserving the chemistry of the backbone and reactive end-group pairs and controlling other experimental variables such as concentration ( Fig.…”