Correlation Among Crystal Structure, Mechanical Behavior, and Tabletability in the Co-Crystals of Vanillin Isomers
Correlation Among Crystal Structure, Mechanical Behavior, and Tabletability in the Co-Crystals of Vanillin Isomers
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DOI：
10.1021/cg5018642
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发表时间：
2015-04-01
影响因子：
3.8
通讯作者：
Reddy, C. Malla
中科院分区：
文献类型：
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作者：
Krishna, G. Rama;Shi, Limin;Reddy, C. Malla
分子材料在医药、食品、精细化工、光电子等领域具有广泛的应用前景，因此其力学性能的调控成为当前研究的热点。本文采用晶体工程的方法，通过与6-氯-2，4-二硝基苯胺（cda）形成共晶体，将四种食品调味剂香草醛异构体从脆性固体转变为软质固体。该系列包括香草醛（货车）、乙基香草醛（evan）、异香草醛（i货车）以及邻香草醛（o货车）与乙二胺的席夫碱（sb-o货车）。所有的共晶采用平面二维（2D）层填料，除了sb-ovan：cda，它采用了一个波纹层填料与滑移面的存在。共晶体的机械性能通过（1）定性方法，（2）纳米压痕，和（3）粉末压制技术进行了研究，这使得成功地建立晶体结构，机械性能和片剂拉伸强度之间的关系。简单的定性机械（变形）测试证实了cda与货车、evan和i货车的共晶中的塑性剪切变形行为，而sb-o货车：cda的共晶由于结构中存在由货车德瓦尔斯相互作用形成的滑移面而显示塑性弯曲。香草醛异构体和它们各自的共晶体的测量的拉伸强度（其遵循以下顺序：sb-o货车：cda > evan >货车> i货车：cda > evan：cda >货车：cda > sb-o货车> i货车）证实了可塑性弯曲的共晶体sb-o货车：cda与所研究的任何其它形式相比显示出压实性能的显著改善。与具有各向同性结构的初始脆性形式相比，新的共晶固体显示出改善的塑性，这是由于其具有促进塑性变形的活性滑移面的各向异性2D层结构，这增强了可压片性，特别是在塑性可弯曲固体中。该研究还表明，弯曲型晶体可能比剪切型和脆性型晶体更适合压片。
Tuning mechanical performance of molecular materials is currently attractive owing to their practical applications in pharmaceutical, food, and fine chemical industries and optoelectronics. Here we employed a crystal engineering approach to transform four food flavouring agents, vanillin isomers, from brittle to soft solids by forming co-crystals with 6-chloro-2,4-dinitroaniline (cda). The series includes vanillin (van), ethylvanillin (evan), iso-vanillin (ivan), as well as a Schiff base of ortho-vanillin (ovan) with ethylene diamine (sb-ovan). All the co-crystals adopt flat two-dimensional (2D) layer packing, except the sb-ovan:cda, which adopts a corrugated layer packing with the presence of slip planes. The mechanical properties of the co-crystals were studied by (1) a qualitative method, (2) nanoindentation, and (3) powder compaction techniques, which allowed for successfully establishing the relationship among crystal structure, mechanical properties, and tablet tensile strength. The simple qualitative mechanical (deformation) tests confirmed plastic shearing deformation behavior in the cda co-crystals with van, evan, and ivan, while the co-crystal of sb-ovan:cda showed plastic bending due to the presence of slip planes formed by van der Waals interactions in the structure. The measured tensile strengths of the vanillin isomers and their respective co-crystals, which followed the order: sb-ovan:cda > evan > van > ivan:cda > evan:cda > van:cda > sb-ovan > ivan, confirmed that the plastically bendable co-crystal, sb-ovan:cda, shows a significant improvement in the compaction properties compared to any other form studied. In contrast to the initial brittle forms with isotropic structures, the new co-crystal solids show improved plasticity due to their anisotropic 2D-layer structures with active slip planes that facilitate the plastic deformation, which enhances tabletability, particularly in the plastic bendable solid. The study also suggests that the bending type crystals are potentially far better suitable for tabletability than the shearing and brittle type crystals.