Studies of Thermotropic Properties and the Mesophase of Mixtures of n-Alkanoates and Perfluoro-n-alkanoates of Dimolybdenum (Mf" bor

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• 作者：David V. Baxter ; Malcolm H. Chisholm ; Matthew A. Lynn ; Elena F. Putilina ; Scott T. Trzaska ; and Timothy Swager
• 刊名：Chemistry of Materials
• 出版年：1998
• 出版时间：July 1998
• 年：1998
• 卷：10
• 期：7
• 页码：1758 - 1763
• 全文大小：95K
• 年卷期：v.10,no.7(July 1998)
• ISSN：1520-5002

文摘

Mixtures of Mo₂(O₂C(CH₂)_nCH₃)₄, where n = 6 (=Oct) and 7 (=Non), form a columnarmesophase upon heating and the crystal-to-liquid crystal phase transition temperatures differlittle from those predicted by the Shroder-van Laar equation for an ideal mixture. TheXRD of the solid sample obtained from cooling a 1:1 mixture of Mo₂(Oct)₄ and Mo₂(Non)₄conformed to a triclinic cell with lattice parameters intermediate between those of the purecompounds. Similarly in the mesophase the intercolumnar separation (d) was an intermediate distance. The phase behavior of mixtures of Mo₂(non)₄ and Mo₂(O₂C(CH₂)₁₀CH₃)₄ [Mo₂(Dod)₄] were more complex, but in all instances a mesophase was observed whereas that ofthe pure Mo₂(Dod)₄ shows only a crystalline solid to isotropic phase transition. Mixtures ofMo₂(Oct)₄ and Mo₂(O₂C(CF₂)₆CF₃)₄ [Mo₂(Oct^f)₄] were also shown to form a columnarmesophase with an intercolumnar separation intermediate between that of the purecompounds. The mesophase is an optically positive material with the largest component ofthe index of refraction coincident with the columnar axis. The solid to mesophase transitiontemperatures varied significantly from that predicted for an ideal mixture. These resultsare discussed on the basis of facile carboxylate scrambling to produce Mo₂(O₂CR)_4-n(O₂CR')_n,where n = 0-4 in both the mesophase and the resultant solid solution.