title: Circular birefringence of banded spherulites.
abstract: Crystal optical properties of banded spherulites of 21 different compounds--molecular crystals, polymers, and minerals--with 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.
authors.affiliation: Department of Chemistry, New York University , 100 Washington Square East, New York, New York 10003.
authors.forename: Xiaoyan
authors.initials: X
authors.lastname: Cui
authors.forename: Alexander G
authors.initials: AG
authors.lastname: Shtukenberg
authors.forename: John
authors.initials: J
authors.lastname: Freudenthal
authors.forename: Shane
authors.initials: S
authors.lastname: Nichols
authors.forename: Bart
authors.initials: B
authors.lastname: Kahr