ABSTRACT The synthesis and characterisation of two homologous series of non-symmetric dimers are reported, the 1-(4-methoxybiphenyl-4ʹ-yl)-6-(4-alkylanilinebenzylidene-4ʹ-oxy)hexanes (MeOB6O.m, m = 1–10) and 1-(4-methoxybiphenyl-4ʹ-yl)-6-(4-alkyloxyanilinebenzylidene-4ʹ-oxy)hexanes (MeOB6O.Om, m = 1–9). All 10 members of the MeOB6O.m series exhibit the conventional nematic phase. At lower temperatures, the members with m = 1–7 formed the twist-bend nematic phase, NTB, whereas for m = 8–10 smectic behaviour replaced the NTB phase. All nine members of the MeOB6O.Om series also show the conventional nematic phase and for m = 1–3, a strongly monotropic NTB phase is also observed. The alkyloxy terminated dimers show the higher values of TNI and TNTB N . For both series, the values of TNI and TNTB N show a modest alternation and in the same sense as m is increased. These observations suggest that the spatial uniformity of molecular curvature is important in driving the formation of the NTB phase. The observation of smectic behaviour is attributed to the molecular inhomogeneity arising from the long terminal alkyl chain driving microphase separation. The transitional behaviour of these series is compared to those of the corresponding cyanobiphenyl-based series and overarching observations discussed. Graphical Abstract

中文翻译：

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分子结构和扭弯向列相：末端链的作用

摘要报道了两个同源系列的非对称二聚体的合成和表征，1-(4-甲氧基联苯-4′-基)-6-(4-烷基苯胺亚苄基-4′-氧基)己烷 (MeOB6O.m, m = 1 –10) 和 1-(4-甲氧基联苯-4′-基)-6-(4-烷氧基苯胺苯亚甲基-4′-氧基)己烷 (MeOB6O.Om, m = 1–9)。MeOB6O.m 系列的所有 10 个成员都表现出传统的向列相。在较低温度下，m = 1-7 的成员形成扭曲弯曲向列相 NTB，而 m = 8-10 的近晶行为取代了 NTB 相。MeOB6O.Om 系列的所有九个成员也显示出常规的向列相，并且对于 m = 1-3，还观察到强单向性 NTB 相。烷氧基封端的二聚体显示出更高的 TNI 和 TNTB N 值。对于这两个系列，TNI 和 TNTB N 的值显示出适度的变化，并且与 m 的增加具有相同的意义。这些观察结果表明，分子曲率的空间均匀性对于推动 NTB 相的形成很重要。近晶行为的观察归因于由长末端烷基链驱动微相分离引起的分子不均匀性。将这些系列的过渡行为与相应的基于氰基联苯的系列的过渡行为和讨论的总体观察进行比较。图形概要 将这些系列的过渡行为与相应的基于氰基联苯的系列的过渡行为和讨论的总体观察进行比较。图形概要 将这些系列的过渡行为与相应的基于氰基联苯的系列的过渡行为和讨论的总体观察进行比较。图形概要