Synthesis of Highly Thermally Stable Daidzein-Based Main-Chain-Type Benzoxazine Resins

Abstract

In recent years, main-chain-type benzoxazine resins have been extensively investigated due to their excellent comprehensive properties for many potential applications. In this work, two new types of main-chain benzoxazine polymers were synthesized from daidzein, aromatic/aliphatic diamine, and paraformaldehyde. Unlike the approaches used synthesizing traditional main-chain-type benzoxazine polymers, the precursors derived from daidzein can undergo a further cross-linking polymerization in addition to the ring-opening polymerization of the oxazine ring. The structures of the new polymers were then studied by 1H nuclear magnetic resonance spectroscopy (NMR) and Fourier-transform infrared spectroscopy (FT-IR), and the molecular weights were determined by using gel permeation chromatography (GPC). We also monitored the polymerization process by differential scanning calorimetry (DSC) and in situ FT-IR. In addition, the thermal stability and flame-retardant properties of the resulting polybenzoxazines were investigated using TGA and microscale combustion calorimeter (MCC). The polybenzoxazines obtained in this study exhibited a very high thermal stability and low flammability, with a Tg value greater than 400 °C, and a heat release capacity (HRC) value lower than 30 J/(g K).

Research Progress in Toughening Modification of Polybenzoxazine

“…[25] Compared with small molecule benzoxazine which using benzoxazine monomer as the polymerization precursor, the main-chain benzoxazine reduces the suspended chain end units and increases crosslink density, thereby improving their thermal, dielectric and mechanical properties. Han et al [27] synthesized two novel main-chain type benzoxazines from daidzein, aromatic/aliphatic diamine, and paraformaldehyde. Daidzein compound possesses two phenolic hydroxyls and a benzopyrone structure which can improve the thermalmechanical properties of thermosets thereby making it an appropriate phenolic resource.…”

“…On the other hand, design and synthesize benzoxazine group terminated molecules can also be used for improving the toughness or for modification of other kinds of thermoset resins. These benzoxazines can be divided into four categories according to their molecular structures: (1) small molecule benzoxazines, [15,23,24] (2) main chain benzoxazines, [25][26][27][28][29] (3) side chain benzoxazines, [30,31] (4) telechelic benzoxazine. [32][33][34] Scheme 2.…”

Thermal properties of polybenzoxazine exhibiting improved toughness: Blending with cyclodextrin and its derivatives

“…The peak at 940 cm À1 was the characteristic absorption peak of the oxazine ring. 36 The peaks at 1025 cm À1 and 1229 cm À1 were the symmetrical and asymmetrical absorption peaks of C-O-C. 37 These characteristic peaks begin to weaken gradually when the temperature was 140 C (Figure 4(a)). This indicated that the ring-opening reaction of the oxazine ring occurred at temperatures 140 C when -CD-MAH was added.…”

Microporous Carbon and Carbon/Metal Composite Materials Derived from Bio-Benzoxazine-Linked Precursor for CO2 Capture and Energy Storage Applications

“…Many BZs derived from renewable, naturally abundant, bio-based phenols (e.g., resveratrol, bisguaiacol-F, sesamol, diphenolic acid, magnolol, eugenol, daidzein, apigenin, guaiacol, naringenin, coumarin, vanillin, sesamol, cardanol, urushiol, and guaiacol) have been easier to prepare, have displayed superior thermal properties and higher cross-linking densities, and have undergone ROP at lower temperatures when compared with those characteristics of BZ resins derived from petroleum compounds [ 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 ]. For example, apigenin-, naringenin-, and daidzein-based bio-BZs have high glass transition temperatures ( T g , up to 360 °C) because they allow additional crosslinking reactions to occur from the olefinic bonds in their molecular structures, leading to highly cross-linked networks after ROP of their BZ units [ 27 , 28 , 29 ]. In addition, the capability of intramolecular hydrogen bonding in these bio-based phenols leads to lower polymerization temperatures, stable latent catalysts, and improved shelf life of such BZ resins [ 27 , 29 ].…”

“…For example, apigenin-, naringenin-, and daidzein-based bio-BZs have high glass transition temperatures ( T g , up to 360 °C) because they allow additional crosslinking reactions to occur from the olefinic bonds in their molecular structures, leading to highly cross-linked networks after ROP of their BZ units [ 27 , 28 , 29 ]. In addition, the capability of intramolecular hydrogen bonding in these bio-based phenols leads to lower polymerization temperatures, stable latent catalysts, and improved shelf life of such BZ resins [ 27 , 29 ].…”