Impact of polymorphism on mechanical properties of molecular crystals: a study of p -amino and p -nitro benzoic acid with nanoindentation
Impact of polymorphism on mechanical properties of molecular crystals: a study of p -amino and p -nitro benzoic acid with nanoindentation
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多晶型对分子晶体力学性能的影响：对氨基和对硝基苯甲酸的纳米压痕研究
DOI：
10.1039/d1ce00041a
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发表时间：
2021
期刊：
影响因子：
3.1
通讯作者：
Gabriele B
中科院分区：
文献类型：
--
作者：
Gabriele B
我们报告的纳米压痕数据的两对多晶型化合物的对氨基苯甲酸（pABA）和对硝基苯甲酸（pNBA）。在每对的两种形式之间的刚度和硬度数据中观察到60%或更高的变化。我们通过周期键链（PBCs）的变化来解释这些观察结果，即连续分子间相互作用强度和性质的变化。借助来自文献的多晶型物的硬度数据，我们然后进一步评估如何使用PBCs来评估和比较多晶型物的机械性能。我们定义了一个新的参数，s-PBC，它量化了最强的PBC相互作用，需要打破，以便允许PBC网络从3D到2D/1D的切换。我们发现，较高的值的s-PBMC，归一化的平均分子体积，通常导致较高的值的机械性能。尽管并非绝对正确，但当比较给定化合物的多晶型物时，这种趋势似乎保持良好，但当比较不同化合物时，这种趋势就不那么明显了。
We report on nanoindentation data for two pairs of polymorphic compounds of p-aminobenzoic acid (pABA) and p-nitrobenzoic acid (pNBA). Variations of 60% or higher are observed in both stiffness and hardness data between the two forms of each pair. We interpret these observations through variations of periodic bond chains (PBCs), i.e. variations in continuous intermolecular interactions strength and nature. Aided with hardness data of polymorphs from the literature, we then further assess how PBCs can be used to assess and compare mechanical properties of polymorphs. We define a new parameter, s-PBC, which quantifies the strongest PBC interaction that needs breaking so as to allow a switch of the PBC network from 3D to 2D/1D. We found that higher values of s-PBCs, normalised by the mean molecular volumes, usually led to higher values of mechanical properties. Although not infallible, this trend seemed to hold well when comparing polymorphs of a given compound, but not so much when comparing across different compounds.