Acid‐Mediated Autocatalysis in Vinylogous Urethane Vitrimers

Abstract

Vitrimers are a class of polymeric materials with outstanding properties. Intramolecular substitution reactions lead to a dynamic exchange within the polymer network which enables thermoreversible stress relaxation in yet permanently crosslinked materials. In this paper, the acid‐mediated autocatalysis is explored as a rearrangement pathway for vinylogous urethane vitrimers. The autocatalysis enables transimination reactions, resulting in a dynamic exchange among the enamine‐one species, without an excess of free amines. Therefore, the enamine‐ones are protonated by a Brønsted acid and turn into electrophilic iminium‐ones, thus enabling fast backward and substitution reactions with water and free amines. This work provides an in‐depth investigation of the mechanism by kinetic studies of selected compounds. In addition, novel elastomeric and thermosetting poly(vinylogous urethane) networks with and without free amine groups and additional para‐toluene sulfonic acid as a Brønsted catalyst are prepared by bulk polymerization of hexane‐1,6‐diylbis(3‐oxobutanoate) and tris(2‐aminoethyl)amine. The underlying exchange mechanisms are determined by stress‐relaxation experiments with stress relaxation times of 0.3–54 000 s at 110 °C.

Polyaddition Synthesis Using Alkyne Esters for the Design of Vinylogous Urethane Vitrimers

“…Furthermore, the reported results are related to the formation of VU in the cis-product, despite the fact that, theoretically and practically, the trans-product can also be formed. 57 Nevertheless, the cis-product is always the major product, due to the extra stabilisation via an internal hydrogen bond, and was therefore chosen to represent the vinylogous urethane moiety in the performed calculations.…”

Aminoesterenamide Achieved by Three‐Component Reaction Heading toward Tailoring Covalent Adaptable Network with Great Freedom

“…This result aligned well with Du Prez et al's and Abetz et al's findings. [49,53,54] The recyclable nature of PSAM@imidazolyl-x was investigated by first grinding the samples into particles, which were used as raw substance for thermal molding (Figure 4a). The procedure was repeated three times and the recycled samples were subjected to tensile tests, dynamic mechanical analysis (DMA), solubility experiments, and FTIR.…”

Blended vinylogous urethane/urea vitrimers derived from aromatic alcohols

“…Aliphatic acetoacetates undergo a selective condensation reaction with primary amines to give a vinylogous urethane. 24,62 However, aromatic acetoacetates show a different reaction behavior due to their variant electron configuration. For the model study, phenylacetoacetate (PH) was mixed with an excess of hexylamine (2 equivalents) in chloroform at room temperature to give the vinylogous urethane phenyl-3-(hexylamino)but-2-enoate (Phe-VUT-Hex) (Figure 2).…”

“…In comparison, the condensation reaction of the aliphatic methylacetoacetate and hexylamine selectively yields the vinylogous urethane compound in all considered solvents and acetic acid as catalyst. 62 In addition, the characteristic exchange reactions of the vinylogous urethane and vinylogous urea compounds with pending free amines were investigated and compared in terms of their activation energies (Figure 4). For this, an excess of four equivalents of a different amine-type were added to the vinylogous urethane/vinylogous urea mixture to ensure a pseudo first order decay during the beginning of the exchange reaction (Equation S1, ESI).…”

“…TREN has already been established as a suitable cross-linker for vinylogous urethane vitrimers and other vitrimer-types. 24,57,66,67 Furthermore, JA is a commercial, trifunctional amine based on poly(propylene oxide), which is used as Please do not adjust margins Please do not adjust margins a cross-linker in several industrial applications, especially epoxy resins.…”