Imidazole derivatives as thermal latent catalyst for thiol-michael reaction thermosetting resins

Gajeles, Ghellyn; Lee, Sangeun

doi:10.1016/j.eurpolymj.2019.109240

Cited by 6 publications

(1 citation statement)

References 40 publications

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“…However, because the addition of a hardening accelerator rapidly causes a curing reaction in which a phenolic resin and an epoxy resin react to give a hardened material, it is difficult to store the raw material for a long duration. To solve this problem, a latent hardening accelerator with high long-term stability at room temperature in raw materials has been developed as a curing agent [ 7 , 8 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 ]. A latent hardening accelerator initiates the reaction by applying an external stimulus such as heat or light; therefore, the curing reaction does not proceed unless these stimuli are applied.…”

Section: Introductionmentioning

confidence: 99%

Theoretical Study of the Reaction Mechanism of Phenol–Epoxy Ring-Opening Reaction Using a Latent Hardening Accelerator and a Reactivity Evaluation by Substituents

2023

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The mechanism of the phenol–epoxide ring-opening reaction using tetraphenylphosphonium-tetraphenylborate (TPP-K) was investigated using the density functional theory (DFT) method. The reaction was initiated by breaking the P-B bond of TPP-K. The generated tetraphenylborate (TetraPB−) reacted with phenol to form a phenoxide ion, which combined with tetraphenylphosphonium (TPP+) to produce the active species, i.e., tetraphenylphosphonium phenolate (TPP-OPh). The phenoxide ion in TPP-OPh nucleophilically attacked the epoxide. Simultaneously, the H atom in the phenolic OH group moved to the O atom of the ring-opened epoxide. The formed phenoxide ion bound to TPP+ again, and TPP-OPh was regenerated. The rate-determining steps in the reaction were the cleavage of the P-B bond and the triphenylborane-forming reaction. The free energies of activation were calculated to be 36.3 and 36.1 kcal/mol, respectively. It is also suggested that these values in the rate-determining steps could be manipulated by substituents introduced on the Ph group of TetraPB−. Based on these results, it is possible to construct new design guidelines for latent hardening accelerators such as TPP-K.

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