Kaolinite, with a chemical formula of Al₂Si₂O₅(OH)₄, is an abundant and broadly available layered clay mineral. The aluminosilicate monolayer of kaolinite is composed of [SiO]₆ macrorings on one side and gibbsite aluminol groups [Al(OH)₃] on the other side. In this study, ethylene glycol (EG) molecules were covalently grafted to the inner surfaces of kaolinite via etherification between EG hydroxyl and gibbsite aluminol groups to obtain a hybrid material, covalently grafted kaolinite (denoted as K-EG-cg). Commonly, the preparation of K-EG-cg via the conventional heating and stirring method takes longer time (ca. 16 hours); however, only ca. 6 hours are required to achieve K-EG-cg using the solvothermal reaction; moreover, the intercalation efficiency or ratio of the product obtained via the solvothermal reaction is comparable to that obtained using the conventionally heating and stirring method. Infrared spectroscopy, thermogravimetric (TG) analysis, and powder X-ray diffraction were performed; the measurements clearly demonstrate that K-EG-cg is a covalently grafted product and not the result of the physical intercalation of kaolinite with EG (abbr. K-EG). Moreover, the hybrid material K-EG-cg showed much higher deintercalation temperature as compared to K-EG. The dielectrics of K-EG-cg was investigated, indicating that this hybrid material showed intrinsic ferroelectric nature, with the spontaneous polarization P_S ≈ 0.018 μC cm⁻², remanent polarization P_r ≈ 0.015 μC cm⁻², and coercive field E_C ≈ 1.045 kV cm⁻¹ at room temperature. This study provides a fresh impetus to achieve kaolinite-based hybrid functional materials via the covalent grafting approach, which can overcome the disadvantage of thermal instability of the intercalated kaolinite.

中文翻译：

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共价接枝高岭石的乙二醇杂化铁电材料的设计与制备

化学式为Al ₂ Si ₂ O ₅（OH）_4的高岭石是一种丰富且广泛使用的层状粘土矿物。高岭石的铝硅酸盐单层由一侧上的[SiO] _6大环和另一侧上的三水铝铝基[Al（OH）₃ ]组成。在这项研究中，乙二醇（EG）分子通过EG羟基和三水铝矾基铝基团之间的醚化作用共价接枝到高岭石的内表面，以获得杂化材料，共价接枝的高岭石（表示为K-EG-cg）。通常，通过传统的加热和搅拌方法制备K-EG-cg需要更长的时间（约16小时）；但是，只有ca。使用溶剂热反应需要6个小时才能达到K-EG-cg；此外，通过以下方法获得的产品的插层效率或比例溶剂热反应与使用常规加热和搅拌方法所获得的相当。进行了红外光谱，热重分析（TG）和粉末X射线衍射。这些测量清楚地表明，K-EG-cg是共价接枝的产物，而不是高岭石与EG的物理插入的结果（简称K-EG）。此外，与K-EG相比，杂化材料K-EG-cg显示出高得多的脱嵌温度。K-EG-CG的电介质进行了研究，表明该混合材料显示出固有的铁电性质，具有自发极化P_小号≈0.018μC厘米^-2，剩余极化P _{- [R} ≈0.015μC厘米^-2和矫顽场Ë _Ç ≈1.045千伏厘米^-1在室温下。这项研究为通过共价接枝方法获得基于高岭石的杂化功能材料提供了新的动力，它可以克服插层高岭石的热不稳定性的缺点。