Latent Catalyst-Containing Naphthoxazine: Synthesis and Effects on Ring-Opening Polymerization

Abstract

A naphthoxazine containing a latent catalyst based on −OH as part of its monomer structure has been synthesized through a simple one-pot reaction at room temperature. The chemical structure of this naphthoxazine monomer has been confirmed by 1H NMR, 13C NMR, and FT-IR and its purity by elemental analysis. Differential scanning calorimetry (DSC) and in situ FT-IR have been used to investigate the active and inactive conditions for the latent catalysis. DSC and thermogravimetric analysis (TGA) studies indicate that this naphthoxazine polymerizes quickly before the monomer evaporation, as is often the case for conventional naphthoxazines, minimizing the monomer loss during polymerization. The intramolecular interactions between the −OH group and oxazine ring and pyrrolidine ring of the monomer have been investigated in detail by using the homonuclear two-dimensional (2D) NMR technique 1H–1H nuclear Overhauser effect spectroscopy (NOESY). The −OH interacts with the N in the pyrrolidine ring and oxazine ring through stable intramolecular hydrogen bonds instead of presenting free −OH at room temperature, leading to the enhanced shelf life of the monomer. The free phenolic −OH initiates and catalyzes the polymerization once the hydrogen-bonded interactions are weakened or disrupted upon increasing temperature, showing a latent catalytic effect.

Well-defined benzoxazine/triphenylamine-based hyperbranched polymers with controlled degree of branching

“…3,29 Benzoxazine (BZ) monomers possess the ability to undergo thermal ring-opening polymerization, without the need for any catalysts and without the formation of byproducts, forming polymers with several unique features (e.g., high chemical resistance, low surface free energy, high ame retardancy) that have drawn the attention of both academia and industry. [30][31][32][33][34][35][36][37] Triphenylamine (TPA) possesses a unique two-photon absorption ability and has been studied and applied in many elds, including optoelectronic devices and electron transition devices. [38][39][40] Hence, we have been interested in combining the properties of BZ and TPA units in polymeric systems.…”

Study of the Effects of Intramolecular and Intermolecular Hydrogen‐Bonding Systems on the Polymerization of Amide‐Containing Benzoxazines

“…Polybenzoxazine is a new category of thermoset materials that has been extensively studied in recent years due to the easy synthesis and outstanding properties . Benzoxazines can be synthesized by Mannich condensation from phenol, amine, and formaldehyde .…”

The Journey of Phenolics from the First Spark to Advanced Materials

“…For example, benzoxazines with −COOH, −OH groups were shown to be effective in reducing the T ROP ca . 10–40 °C . The second major approach is to mix benzoxazines with Lewis, mineral, organic acids or molecules having a sort of acidity to catalyze the curing.…”

“…10-40°C. [67,[73][74][75] The second major approach is to mix benzoxazines with Lewis, mineral, organic acids or molecules having a sort of acidity to catalyze the curing. And recently, latent catalyst systems come into prominence since these catalysts are dormant at room temperature, but activated upon heating, making it easier to prepare catalyst-benzoxazine formulations that are suitable for long term storage.…”