Calorimetric and Spectroscopic Evidence of Chain-Melting in Smectic E and Smectic A Phases of 4-Alkyl-4'-isothiocyanatobiphenyl (nTCB)
Calorimetric and Spectroscopic Evidence of Chain-Melting in Smectic E and Smectic A Phases of 4-Alkyl-4'-isothiocyanatobiphenyl (nTCB)
复制标题
4-烷基-4-异硫氰酸联苯 (nTCB) 近晶 E 相和近晶 A 相链熔化的量热和光谱证据
DOI：
10.1021/jp303972s
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发表时间：
2012
期刊：
影响因子：
3.3
通讯作者：
S. Urban & K. Saito
中科院分区：
文献类型：
--
作者：
Y. Yamamura;T. Adachi;T. Miyazawa;K. Horiuchi;M. Sumita;M. Massalska-Arodz;S. Urban & K. Saito
为了证实4-n-烷基-4 ′-异硫氰酸基联苯（nTCB，n：烷基中的碳原子数）在软晶相、近晶E（SmE）相中的熔融状态，对其进行了热力学和光谱分析. 11 TCB和12 TCB（除近晶E相外还含有近晶A相）的DSC结果表明，它们从有序结晶（OC）相到SmE相的转变熵（ΔtrsS）与链长的关系与nTCB（n= 4-10）的趋势一致，而11 TCB和12 TCB在SmE到SmA和SmA到各向同性液体（IL）相变时的Δ trsS没有观察到链长依赖性。记录了6个化合物（n= 2，3，5，8，10和12）的FT-IR光谱的温度依赖性。CH伸缩模式的链表现出更明显的变化，在从OC到SmE相的过渡比在从SmE相到IL或SmA相的过渡。这些结果表明，在SmE相的烷基链是熔融的IL。从熵的角度讨论了nTCB分子从OC经各向异性中间相到IL的无序化过程。
To confirm the molten state of the alkyl chain in soft crystalline phase, smectic E (SmE) phase, thermodynamic and spectroscopic analyses were performed on 4-n-alkyl-4′-isothiocyanatobiphenyl (nTCB,n: the number of carbon atoms in the alkyl group). DSC results of 11TCB and 12TCB, having extra smectic A phase besides smectic E phase, show that their chain-length dependence of entropies of transition (ΔtrsS) from the ordered crystalline (OC) phase to the SmE phase matches the trend found fornTCB (n= 4–10), while no chain-length dependence is observed in ΔtrsSat the SmE-to-SmA and SmA-to-isotropic liquid (IL) phase transitions in 11TCB and 12TCB. Temperature dependences of FT-IR spectra of six compounds (n= 2, 3, 5, 8, 10, and 12) were recorded. The CH stretching modes of the chain exhibited more pronounced change at the transition from the OC to the SmE phase than at the transition from the SmE phase to the IL or SmA phase. These results indicate that the alkyl chain is molten in the SmE phase as in IL. The disordering process ofnTCB molecules from the OC to IL via anisotropic mesophases is discussed in terms of entropy.