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).
Highlights
Introduction1,3-Benzoxazine monomers are new types of thermosetting resins that have attracted wide attention over the past few decades due to the outstanding molecular design flexibility [1,2,3,4]
Research School of Polymeric Materials, School of Materials Science and Engineering, Jiangsu University, Department of Chemistry, University of Leicester, Leicester LE1 7RH, UK
Synthesis of the Main-Chain-Type Benzoxazine Starting from Daidzein, 4,40 -Diaminodiphenylmethane and Paraformaldehyde (Abbreviated as Poly(Dd-Ddm)Main )
Summary
1,3-Benzoxazine monomers are new types of thermosetting resins that have attracted wide attention over the past few decades due to the outstanding molecular design flexibility [1,2,3,4]. In addition to the unique advantage of benzoxazine monomers, polybenzoxazines possess many excellent properties, such as near-zero shrinkage during polymerization [5], high thermal stability [6,7,8,9], low surface free energy [10,11], self-healing capacity [12], low dielectric constant [9,13,14], and low flammability [15,16,17]. The detailed synthetic methods and the properties of polybenzoxazines derived from the new obtained main-chain-type benzoxazine resins are reported
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