高透明高韧性黏土/聚乙烯醇人造贝壳

Highly Transparent and Tough Clay / Poly( vinyl alcohol) Artificial Nacre

天然贝壳由碳酸钙片和少量生物聚合物组成,同时具有高的强度和韧性.这些优异的力学性能主要归因于高的碳酸钙片含量、精心设计的层状结构、强的界面粘结和碳酸钙片适当的长径比,使得贝壳以片拔出的形式断裂,导致优异的强度和韧性.受天然贝壳结构和力学性能之间关系的启发,采用蒸发诱导自组装方法制备了黏土/聚乙烯醇人造贝壳,其中黏土的含量为52 wt%.扫描电镜、透射电镜和X射线衍射证实了其层状结构.红外光谱证实黏土和聚乙烯醇之间形成氢键.拉伸测试测得人造贝壳强度为（90.2±8.0）MPa,与天然贝壳（80~135 MPa）相当;人造贝壳断裂应变高达（14.7±2.3）%,远高于天然贝壳（约2%）;人造贝壳拉伸韧性高达（10.6±3.0）MJ/m^3.此外,所制备的人造贝壳透明,透明度高达90%以上.

Inspired by the relationship between microstructure and mechanical properties of natural nacre,clay / poly（ vinyl alcohol） artificial nacre was prepared through evaporation-induced assembly of poly（ vinyl alcohol） / coated clay nanoplatelets. The clay loading in the artificial nacre is determined as 52 wt% by thermogravimetric analysis. A well-defined layered structure is proved by scanning electronic microscopy,transmission electronic microscopy and X-ray diffraction. FTIR proves that hydrogen bond is formed between clay and PVA. Tensile test results show that the strength of the artificial nacre is about（ 90. 2 ± 8. 0） MPa,comparable to that of natural nacre（ 80 ~ 135 MPa）. Importantly,the elongation at break and tensile toughness reach（ 14. 7 ± 2. 3） % and（ 10. 6 ± 3. 0） MJ / m^3,respectively,which are much higher than those of the reported bio-inspired layered montmorillonite / polymer nanocomposites. The improved strength is attributed to the high clay loading,ordered layered structure and strong interfacial adhesion. Interestingly,appropriate aspect ratios of clay platelets enable the artificial nacre to fail in the form of clay platelet pull-out and thus leads to high toughness. In addition,the artificial nacre is transparent because of reduced light scattering,arising from ordered layered structure and small diameter of the used clay. The transparency of the artificial nacre is more than 90%.