Ring‐Opening Oligomerization Mechanism of a Vanillin‐Furfurylamine‐Based Benzoxazine and a Mono‐Azomethine Derivative

Abstract

Exploring the ring‐opening polymerization (ROP) mechanism of benzoxazines is a fundamental issue in benzoxazine chemistry. Though some research papers on the topic have been reported, the ROP mechanism of mono‐benzoxazines is still elusive. The key point for mechanistic studies is to determine and characterize the structure and formation pathways of the products generated in ROP. In this paper, the ROP of a vanillin‐furfurylamine‐based benzoxazine and a mono‐azomethine derivative is studied with differential scanning calorimetry, fourier transform infrared spectroscopy, nuclear magnetic resonance, and electrospray ionization mass spectrometry, respectively. The results show that the products consist of a range of cationic species, zwitterions, fragments, and series of cyclic and linear oligomers of varying molecular sizes. It is proposed that both mono‐benzoxazines undergo thermally activated cationic ring‐opening oligomerization via zwitterion intermediates. Upon thermal induction, multi‐bond‐cleavage takes place to form various zwitterionic intermediates, which react with a monomer, a fragment, or a second zwitterion by several pathways to generate cyclic and linear oligomers.

Biobased Polybenzoxazine Vitrimer with Imine Bonds: Shape Memory, Reprocessing, and Degradation

“…Hamernik et al prepared a degradable polybenzoxazine with imine bonds by 4-hydroxybenzaldehyde, benzylamine, and diamines . To reduce the use of traditional fossil-based raw materials and achieve the goal of sustainable development, a variety of biobased raw materials have been applied to the preparation of polybenzoxazines, such as eugenol, − vanillin, , phloretic acid, cardanol, resveratrol, and apigenin as phenol resources, and furfurylamine, , stearylamine, and dehydroabietylamine as amine resources. Among them, vanillin is an aromatic aldehyde with a phenolic hydroxyl group, which is suitable for the preparation of biobased vitrimer containing imine bonds. , In recent years, a variety of biobased polybenzoxazine vitrimers were prepared by the introduction of dynamic covalent bonds such as disulfide bonds, ester bonds, , and acetal bonds …”