Study of the Diels–Alder and retro-Diels–Alder reaction between furan derivatives and maleimide for the creation of new materials

Abstract

This study showed a way to increase the endo/exo ratio in favor of the endo adduct in furan derivatives/maleimide systems.

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

“…Although the conversion at 70 and 80°C was similar, there was an important difference between the ratio of exo/endo adduct. Due to the fact that exo adduct is thermodynamically favoured [5,6], the ratio is increasing with temperature and time. At 60°C endo adduct was the predominant product and there was no significant increase in ratio by time indicating that temperature was not yet in favour of exo emergence.…”

“…While the endo compound is kinetically favoured, the exo is thermodynamically favoured and thus more stable [5,6]. The aim of the detailed study of the thermal behaviour of the PMI/ GF mixture is its possible further application as a self-healing polymer network.…”

“…On the other hand there might be a reason, why there is not yet a known self-remendable benzoxazine polymer material with DA reaction based remendability. The reason being high curing temperature needed for polymerization of benzoxazines [31,32], usually quite above the temperature of rDA reaction (~100°C) of normally used diene and dienophile system (furan and maleimide) [5,6]. This means that DA connections are broken and starting compounds are formed.…”

“…DA adduct is the mixture of two diastereomers called endo and exo adducts. Temperature of the rDA reaction leading to the appearance of the endo adduct is typically lower than that of the exo adduct [5,6]. Due to the thermal reversibility of DA reactions, they are frequently applied in the production of remendable and recyclable materials [7][8][9][10].…”

“…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].…”