Abstract
Reversible Diels–Alder (DA) type networks were prepared from furan and maleimide monomers of different structure and functionality. The factors controlling the dynamic network formation and their properties were discussed. Evolution of structure during both dynamic nonequilibrium and isothermal equilibrium network formation/breaking was followed by monitoring the modulus and conversion of the monomer. The gelation, postgel growth, and properties of the thermoreversible networks from tetrafunctional furan (F4) and different bismaleimides (M2) were controlled by the structure of the maleimide monomer. The substitution of maleimides with alkyl (hexamethylene bismaleimide), aromatic (diphenyl bismaleimide), and polyether substituents affects differently the kinetics and thermodynamics of the thermoreversible DA reaction, and thereby the formation of dynamic networks. The gel-point temperature was tuned in the range Tgel = 97–122 °C in the networks of the same functionality (F4-M2) with different maleimide structure. Theory of branching processes was used to predict the structure development during formation of the dynamic networks and the reasonable agreement with the experiment was achieved. The experimentally inaccessible information on the sol fraction in the reversible network was received by applying the theory. Based on the acquired results, the proper structure of a self-healing network was designed.
Highlights
The polymer networks form basis of materials with a broad range of applications
We studied kinetics of the DA reaction of tetrafunctional furan monomer F4D2000 with three maleimide monomers
The kinetics of the reversible reaction at different temperatures was followed by FTIR both in the solution (6% in dioxane) and in the bulk system
Summary
The polymer networks form basis of materials with a broad range of applications. They show a better environmental resistance, mechanical, thermal, and generally high performance properties for application in structural materials, coatings, adhesives or in composite systems. Contrary to thermoplastics, they are not reprocessable and recyclable. The crucial requirement for new polymer materials involves a lengthening of a material service time and possibility of recycling, while keeping their excellent properties. Self-healing of polymer network materials is a great challenge for both basic and applied research. The covalent reversible networks meet these requirements. They are suitable for different applications, as reshapeable thermosets, for bonding/de-bonding adhesives, for self-healing, etc
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