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首页> 外文期刊>Journal of Crystal Growth >Crystal Growth Of α And γ Glycine Polymorphs And Their Polymorphic Phase Transformations
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Crystal Growth Of α And γ Glycine Polymorphs And Their Polymorphic Phase Transformations

机译：α和γ甘氨酸多晶型物的晶体生长及其多态相变

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摘要

The single crystals of α and γ polymorphs of glycine were grown from aqueous solutions at ambient conditions. The metastable α-form was crystallized from pure aqueous solution and the stable γ-form from aqueous solution in the presence of a critical concentration of a selective additive sodium chloride. Attempt to grow sizable β-form single crystals were not successful because of their high instability. In stability terms at ambient conditions these three glycine polymorphs are like this: β < α < γ. The form of crystallization was confirmed by X-ray powder diffraction (XRD). The α- and β-forms crystallize in the monoclinic system with centrosymmetric space groups P2_1.n and P2_1, respectively, and the y-form crystallizes in trigonal-hexagonal system with non-centrosymmetric space group P3_2. At high-humidity conditions, the room temperature polymorphic phase transformations from α to γ and solution-mediated phase transformation from β to α were confirmed by XRD. The transformation from γ to α while heating well above the room temperature observed at around 179 ℃ was recorded by thermogravimetry (TG) and differential thermal analysis (DTA) and confirmed by differential scanning calorimetry (DSC). The morphology of the grown polymorphs were analysed by goniometry. CHN analysis shows the non-existance of sodium chloride species in the grown γ-glycine single crystals. The optical transparancy of the γ-form was recorded by UV-vis-Near 1R spectroscopy.
机译：甘氨酸的α和γ多晶型物的单晶是在环境条件下从水溶液中生长的。在临界浓度的选择性添加剂氯化钠存在下，亚纯的α-形式从纯水溶液中结晶，稳定的γ-形式从水溶液中结晶。由于其高度的不稳定性，尝试生长可观的β型单晶没有成功。在环境条件下的稳定性方面，这三种甘氨酸多晶型如下：β<α<γ。通过X射线粉末衍射（XRD）确认结晶形式。 α型和β型分别在具有中心对称空间组P2_1.n和P2_1的单斜晶系中结晶，而y型在具有非中心对称空间组P3_2的三角六边形体系中结晶。在高湿度条件下，通过XRD证实了室温下从α到γ的多态相转变和溶液介导的从β到α的相变。通过热重法（TG）和差示热分析（DTA）记录了在远高于179℃观察到的室温下从γ到α的转变，并通过差示扫描量热法（DSC）确认。通过测角法分析了生长的多晶型物的形态。 CHN分析表明，在生长的γ-甘氨酸单晶中不存在氯化钠物质。通过UV-vis-Near 1R光谱记录γ-形式的光学透明性。

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