On the Circular Birefringence of Polycrystalline Polymers: Polylactide.
The circular birefringence of polycrystalline polymers is invariably obscured by strong linear birefringence. To parse the two mechanisms of light retardation, polycrystalline spherulites of polylactide enantiomers were analyzed by Mueller matrix microscopy. Polymer films are barely optically active...
| Publicado en: | Journal of the American Chemical Society Vol. 133; no. 35; pp. 13848 - 13852 |
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| Autores principales: | , , , |
| Formato: | Artículo |
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American Chemical Society
9/7/2011
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| Acceso en línea: | Ver este registro en EBSCOhost |
| fields | @attributes: recordID: 1 pdfLink: plink: https://search.ebscohost.com/login.aspx?direct=true&db=hlh&AN=66777644&site=ehost-live header: @attributes: shortDbName: hlh uiTerm: 66777644 longDbName: Humanities International Complete uiTag: AN controlInfo: bkinfo: jinfo: jid: 00027863 ACS jtl: Journal of the American Chemical Society issn: 00027863 maglogo: N pubinfo: dt: 9/7/2011 vid: 133 iid: 35 pid: 997 pub: American Chemical Society artinfo: ui: 66777644 10.1021/ja205159u ppf: 13848 ppct: 4 formats: tig: atl: On the Circular Birefringence of Polycrystalline Polymers: Polylactide. aug: au: Ye, Hai-Mu Jun Xu Freudenthal, John Kahr, Bart affil: Department of Chemical Engineering, Tsinghua University, Beijing 100084, China Department of Chemistry, New York University, 100 Washington Square East, New York, New York 10003, United States su: Double refraction Polycrystals Enantiomers Microreactors Metamaterials sug: subj: Double refraction Polycrystals Enantiomers Microreactors Metamaterials ab: The circular birefringence of polycrystalline polymers is invariably obscured by strong linear birefringence. To parse the two mechanisms of light retardation, polycrystalline spherulites of polylactide enantiomers were analyzed by Mueller matrix microscopy. Polymer films are barely optically active in normal incidence, but if illuminated obliquely they become strongly optically active. Opposite hemispheres have oppositely signed circular birefringence. The sign is independent of the enantiomer but dependent on the sense of the sample's tilt. These observations are consistent with light path inhomogeneities resulting from stacked, mis-oriented lamellae. Chiroptical commonalities based on symmetry arguments are discussed among polylactide, a single oriented water molecule, and microfabricated metamaterial arrays, as well as the first physical model of optical activity, Reusch's pile of mica plates. The latter model provides the best explanation of the circular birefringence of polylactide spherulites. The only data on the optical rotation of crystalline polymers to date come from ostensible single crystals of polylactide. The enormous, anisotropic optical rotations observed previously are in quantitative agreement with misoriented lamellae observed here. Limitations of parsing circularly birefringent systems into those showing 'natural optical activity' and those others, somehow 'unnatural', are discussed. pubtype: Academic Journal doctype: Article src: R language: English refInfo: copyright: @attributes: flag: Y dt: @attributes: year: 2011 holdings: @attributes: islocal: N |
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