Intermolecular organisation of triphenylenebased discotic mesogens by interdigitation of alkyl chains
作者:Matthew T. Allen、Siegmar Diele、Kenneth D.M. Harris、Torsten Hegmann、Benson M. Kariuki、Dirk Lose、Jon A. Preece、Carsten Tschierske
DOI:10.1039/b006916g
日期:——
Two series of hexakis(alkyloxy)triphenylenes have been synthesised
and characterised. All materials contain two different lengths of n-alkyloxy
chains. Series I
(C5Cn)
materials contain three –OC5H11 chains and three –OCnH2n + 1 chains. Series II
(CmCn)
materials contain three –OCmH2m + 1
chains and three –OCnH2n + 1
chains, such that m + n
= 10.
Hexagonal columnar mesophases are observed in Series I for n ≥ 3
and, in Series II, for C5C5 and C6C4.
Investigation by XRD shows that, within Series I, increasing the
Cn chain length increases the intercolumnar spacing. Furthermore,
the intercolumnar spacings for constitutional isomers are identical. The difference
in the lengths of the two types of alkyl chain at the periphery of the molecules
is defined as the Interdigitation Length (IL) and is a measure of
the maximum extent of interdigitation that is possible between neighbouring
molecules. Series I and II materials have been studied to
probe the effect of IL on the change in enthalpy (ΔHCol–I)
and entropy (ΔSCol–I) for the mesophase
to isotropic liquid phase transition. In contrast to CxCx
materials, which show a decrease in ΔHCol–I
and ΔSCol–I with increasing chain length, Series
I and II mesogens all exhibit ΔHCol–I
and ΔSCol–I values similar to those of long
chain CxCx materials, irrespective
of chain length.
已合成并表征两系列六烷基醚三苯基烯。所有材料均包含两种不同长度的n-烷氧基链。系列I (C5Cn) 材料包含三条 –OC5H11 链和三条 –OCnH2n + 1 链。系列II (CmCn) 材料包含三条 –OCmH2m + 1 链和三条 –OCnH2n + 1 链,其中 m + n = 10。系列I在 n ≥ 3 时观察到六方柱状介相,而系列II则在 C5C5 和 C6C4 时观察到。XRD研究显示,在系列I中,增加Cn链的长度会增加柱间距。此外,构象异构体的柱间距是相同的。分子外周两种烷基链长度的差异被定义为交错长度(IL),它是衡量相邻分子之间最大交错程度的指标。研究了系列I和II材料,以探讨IL对介相到各向同性液相转变的焓变化(ΔHCol–I)和熵变化(ΔSCol–I)的影响。与CxCx材料不同,CxCx材料在链长增加时ΔHCol–I和ΔSCol–I均减少,而系列I和II的介晶体在ΔHCol–I和ΔSCol–I值上都与长链CxCx材料相似,而与链长无关。