Despite recent advances in polybenzoxazines (PBzs), especially of sustainable origin, the lowering of the curing temperature still remains a challenge in addressing their exploration in low-temperature processing applications. Innovative iron-based catalysts which are naturally abundant, cost-effective, and with larger surface area could demonstrate a practical, economic and facile approach for the development of iron NPs–polybenzoxazine composites. Here we propose an approach to develop a composite based on smartly-capped iron nanoparticles (NPs) and agro-waste phenolic-sourced cardanol benzoxazine monomer as a one-step solution with the benefits of lowering the curing temperature and providing superparamagnetism. NPs are smartly designed with a variation in the nature of the functionality in the capping agent and are characterized by thermogravimetry analysis (TGA), Fourier transform infrared (FTIR), powder X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The NPs showed a spherical shape of ∼10 nm in size with appreciable magnetic characteristics. Both iron ions and available functionalities in the capping agent endow benefits in lowering the curing temperature of cardanol benzoxazine (64 °C), and enhancing its maximum thermal stability (34 °C), as determined by differential scanning calorimetry (DSC) and TGA, respectively. In addition, the nature of the chemical linkages in the polybenzoxazine network and the initial growth in the molecular weight of the polymer were found to be influenced by iron NPs, as supported by FTIR, nuclear magnetic resonance (¹H-NMR), UV-visible (UV-vis) spectroscopy, and gel permeation chromatography (GPC). The capping-agent-facilitated NPs distribution in the polybenzoxazine matrix was determined by atomic force microscopy (AFM). Polymer nanocomposites even with a 5 wt% loading of NPs showed good magnetic saturation and superparamagnetic behavior. The present work demonstrated a one-step solution with the incorporation of NPs in a benzoxazine monomer accounting for modification in the properties of polybenzoxazine composites with the benefits of magnetism.

中文翻译：

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基于智能设计的铁纳米颗粒和腰果酚苯并恶嗪的低温可固化超顺磁性复合材料的可持续性一步策略†

尽管聚苯并恶嗪（PBzs）的最新进展，尤其是可持续发展的聚苯并恶嗪（PBzs）的进展，降低固化温度仍然是解决其在低温加工应用中的探索难题。自然丰富，具有成本效益且表面积较大的创新铁基催化剂可以证明开发铁NPs-聚苯并恶嗪复合材料的实用，经济和便捷的方法。在这里，我们提出了一种基于智能封端的铁纳米颗粒（NPs）和农残酚源的腰果酚苯并恶嗪单体的复合材料开发方法，该方法具有降低固化温度和提供超顺磁性的优点。NP的设计巧妙，其封端剂的功能性质有所变化，并具有热重分析（TGA），傅立叶变换红外（FTIR），粉末X射线衍射（XRD），扫描电子显微镜（SEM），和透射电子显微镜（TEM）。NP显示出约10nm大小的球形，并具有明显的磁特性。通过差示扫描量热法（DSC）和TGA确定，铁离子和封端剂中的可用官能团均有助于降低腰果酚苯并恶嗪的固化温度（64°C），并提高其最大热稳定性（34°C），分别。此外，¹ H-NMR），UV-可见（UV-vis）光谱和凝胶渗透色谱（GPC）。通过原子力显微镜（AFM）确定了封端剂促进的NPs在聚苯并恶嗪基质中的分布。甚至具有5重量％的NP的负载量的聚合物纳米复合材料也表现出良好的磁饱和和超顺磁性能。目前的工作证明了一种将NPs掺入苯并恶嗪单体的一站式解决方案，这说明了利用磁性的优势可以改变聚苯并恶嗪复合材料的性能。