Branching of the Perfluorinated Chain Influences the Liquid-Crystalline Properties of Semifluorinated Alkanes: Perfluorooctyl- and Perfluoroisononyl-n-Alkanes—a Comparative Study
Branching of the Perfluorinated Chain Influences the Liquid-Crystalline Properties of Semifluorinated Alkanes: Perfluorooctyl- and Perfluoroisononyl-n-Alkanes—a Comparative Study
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DOI：
10.1080/15421400600700430
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发表时间：
2006-12
影响因子：
0.7
通讯作者：
M. Broniatowski;P. Dynarowicz-Łątka;W. Witko-
中科院分区：
文献类型：
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作者：
M. Broniatowski;P. Dynarowicz-Łątka;W. Witko-
合成了两个系列的全氟链长相当但端基结构不同的半氟化正构烷烃，即全氟辛基正构烷烃[F-（CF 2）8-（CH 2）n-H，简称F8 Hn]和全氟异壬基正构烷烃[（CF 3）2CF（CF 2）6-（CH 2）n-H，简称iF 9 Hn]。通过差示扫描量热法（DSC），对样品的加热和冷却的热性能进行了分析。用偏光显微镜研究了合成的半氟烷烃的织构。与先前研究的全氟癸基正烷烃类似，含有少于12个亚甲基的全氟辛基正烷烃形成近晶B相。F8 H8、F8 H9和F8 H10表现出过冷的趋势，并且即使在低于转变温度时也保持近晶B有序。对于F_8H_（11），观察到了从近晶B向三维晶体结构的相变，表现为快速再结晶。具有12个或更多个亚甲基的全氟辛基正烷烃不形成液晶相。与全氟辛基正烷烃相反，全氟异壬基正烷烃不能够形成液晶相，无论氢化部分长度和实验条件如何。
Two series of semifluorinated-n-alkanes (SFAs) of comparable perfluorinated chain length but different terminal group constitution, namely perfluorooctyl-n-alkanes [F–(CF2)8–(CH2)n–H, in short F8Hn] and perfluoroisononyl-n-alkanes [(CF3)2CF(CF2)6–(CH2)n–H, in short iF9Hn] were synthesized. Their thermal properties were analyzed by means of differential scanning calorimetry (DSC), on both heating and cooling of the samples. The textures of the synthesized semifluorinated alkanes were investigated with the microscopy in polarized light. Similar to previously investigated perfluorodecyl-n-alkanes, perfluorooctyl-n-alkanes containing fewer than 12 methylene groups form smectic B phase. F8H8, F8H9, and F8H10 show a tendency to supercool and preserve smectic B ordering even below the transition temperature. For F8H11, the phase transition from smectic B to 3D crystal structure, manifesting itself as a rapid recrystallization, has been observed. Perfluorooctyl-n-alkanes of 12 or more methylene groups do not form liquid-crystalline phases. In contrast to perfluorooctyl-n-alkanes, perfluoroisononyl-n-alkanes are not capable of liquid-crystalline phase formation, regardless of the hydrogenated moiety length and the experimental conditions.