A key requirement for the exploitation of two-dimensional (2D)-crystals in the field of composites relies on their large-scale production. In this respect, liquid phase exfoliation of layered-crystals is emerging as one of the most promising approaches for the scalable production of high-quality 2D-crystals. However, the dependence of the 2D crystal flakes morphology, i.e. thickness and lateral size, on the mechanical properties of the polymer composites is not fully understood yet. Herein, we tackle this issue by designing an environmentally friendly approach, based on the exfoliation of bulk hexagonal-boron nitride (h-BN), widely used as filler in polymer composites for its high intrinsic stiffness, i.e. approaching 1 TPa, in a water/surfactant solution with controlled thickness and lateral size by using cascade ultra-centrifugation. Our approach allows us to obtain two populations of flakes with aspect ratio, i.e. lateral size over thickness, equal to 250 and 350, respectively. The h-BN flakes with tuned aspect ratio are subsequently used as filler in a polycarbonate (PC) matrix by exploiting solution blending in 1,3-dioxolane, a solvent with Hansen’s solubility parameters matching the ones of h-BN, thus enhancing the dispersion of the filler inside the matrix, as evaluated by Raman mapping. We tested the composite mechanical properties finding that flakes with higher aspect ratio show superior reinforcements in terms of both ultimate tensile strength and Young’s modulus, compared with their lower aspect ratio counterparts. As example, at 0.1 wt% of loading, the difference in reinforcement in terms of Young’s Modulus is of 56 MPa, being the increment, compared to pristine PC, of ∼22% for composites produced with higher aspect ratio fillers, whereas it is instead of only ∼17% for lower aspect ratio fillers.

在复合材料领域开发二维 (2D) 晶体的关键要求依赖于它们的大规模生产。在这方面，层状晶体的液相剥离正在成为可扩展生产高质量 2D 晶体的最有前途的方法之一。然而，二维晶体薄片形态（即厚度和横向尺寸）对聚合物复合材料机械性能的依赖性尚不完全清楚。在这里，我们通过设计一种环保方法来解决这个问题，该方法基于块状六方氮化硼（h-BN)，广泛用作聚合物复合材料的填料，因为它具有高固有刚度，即接近 1 TPa，在水/表面活性剂溶液中使用级联超离心控制厚度和横向尺寸。我们的方法使我们能够获得具有纵横比（即横向尺寸与厚度）分别等于 250 和 350 的两组薄片。通过利用 1,3-二氧戊环中的溶液共混，具有调节纵横比的h -BN 薄片随后被用作聚碳酸酯 (PC) 基质中的填料，1,3-二氧戊环是一种具有与h相匹配的 Hansen 溶解度参数的溶剂。-BN，从而增强了填料在基质内的分散，如通过拉曼映射评估的那样。我们测试了复合材料的机械性能，发现与较低纵横比的薄片相比，具有较高纵横比的薄片在极限拉伸强度和杨氏模量方面表现出优异的增强作用。例如，在 0.1 wt% 的负载量下，增强材料的杨氏模量差异为 56 MPa，与原始 PC 相比，对于使用更高纵横比填料生产的复合材料而言，增量约为 22%，而对于低纵横比填料，仅为 17%。