Circular Birefringence of Banded Spherulites

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• 作者：Xiaoyan Cui ; Alexander G. Shtukenberg ; John Freudenthal ; Shane Nichols ; Bart Kahr
• 刊名：Journal of the American Chemical Society
• 出版年：2014
• 出版时间：April 9, 2014
• 年：2014
• 卷：136
• 期：14
• 页码：5481-5490
• 全文大小：725K
• 年卷期：v.136,no.14(April 9, 2014)
• ISSN：1520-5126

文摘

Crystal optical properties of banded spherulites of 21 different compounds鈥攎olecular crystals, polymers, and minerals鈥攚ith helically twisted fibers were analyzed with Mueller matrix polarimetry. The well-established radial oscillations in linear birefringence of many polycrystalline ensembles is accompanied by oscillations in circular birefringence that cannot be explained by the natural optical activity of corresponding compounds, some of which are centrosymmetric in the crystalline state. The circular birefringence is shown to be a consequence of misoriented, overlapping anisotropic lamellae, a kind of optical activity associated with the mesoscale stereochemistry of the refracting components. Lamellae splay as a consequence of space constraints related to simultaneous twisting of anisometric lamellae. This mechanism is supported by quantitative simulations of circular birefringence arising from crystallite twisting and splaying under confinement.