Monoclinic and Triclinic δ-Clathrates of Syndiotactic Polystyrene

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• 作者：Oreste Tarallo ; Vittorio Petraccone ; Alexandra R. Albunia ; Christophe Daniel ; Gaetano Guerra
• 刊名：Macromolecules
• 出版年：2010
• 出版时间：October 26, 2010
• 年：2010
• 卷：43
• 期：20
• 页码：8549-8558
• 全文大小：1170K
• 年卷期：v.43,no.20(October 26, 2010)
• ISSN：1520-5835

文摘

The paper compares X-ray diffraction patterns of δ-clathrates of s-PS with a large number of guests, having molecular volume in the range 0.058−0.195 nm³, mainly focusing on the distance between the ac layers of enantiomorphous polymer helices (d₀₁₀), as precisely evaluated by measurements on films exhibiting the ac uniplanar orientation. The reported data and the crystal structure determination of the δ-clathrates with dinitrobenzene and dibenzofuran allow concluding that beside the already known large number of δ-clathrates of s-PS with monoclinic unit cells there is also a large number δ-clathrates of s-PS with triclinic unit cells. In particular, monoclinic or triclinic δ-clathrates are generally obtained with guests whose molecular volume is lower or higher with respect to the cavity of the δ nanoporous crystalline form (≈ 0.125 nm³). Small guests are easily accommodated in the cavities of the δ phase, thus maintaining its monoclinic unit cell and P2₁/a symmetry. Bulky guests, on the contrary, can be accommodated by substantial changes of the structural organization of the starting δ nanoporous form, leading to the occupation of only half of the cavities initially present while the other half is lost. This new kind of structural organization of the triclinic δ clathrates allows the inclusion of guest molecules definitely bigger than until now expected, although it halves the maximum guest/styrenic-unit molar ratio, which is reduced from the usual 1/4 to 1/8.