Preorganised effects of a tetramesogenic supermolecule on supramolecular assembly in the liquid crystalline phases

Monolayer to Interdigitated Partial Bilayer Smectic C Transition in Thiophene-Based Spacer Mesogens: X-ray Diffraction and 13C Nuclear Magnetic Resonance Studies

“…Among these, for the linear conformation (Figure A), the L value is nearly double that of the other two. The conventional linear symmetrical dimers are in general observed to exhibit intercalated phases with a typical d / L ratio of 0.5. − This is, however, not considered as a possibility in our case, as the central thiophene dicarboxylate unit is expected to promote for the molecule a bent shape rather than a linear shape for the reason that the bend angle of 2,5-thiophene dicarboxylate is typically 145° . It was shown previously that, without the flexible spacer and only with a thiophene unit connecting the two arms, the molecule can be classified as a bent core mesogen and has a V shape.…”

“…Molecular mesogens containing flexible spacers commonly known as dimers, trimers, and oligomers have gained importance in view of their unusual mesophase characteristics as well as their structural resemblance to mesogenic polymers. − The construction of dimers/oligomers follows the principle of connecting two or more rigid cores through flexible spacers with terminal alkoxy chains at both the ends. , The remarkable feature of these dimers/oligomers in contrast to conventional low molar mass mesogens (calamitic mesogens) is the dependency of mesophase characteristics on the length and the parity of the spacer. − The recent past witnessed growing interest in symmetric and nonsymmetric trimers in which the flexible spacer is connected to the central rigid unit. − These mesogens differ from the classical dimers in the sense that the center part of the mesogen is made up of an anisometric rigid ring rather than a flexible methylene unit often employed for realizing dimers. Among the nonsymmetric trimers, those based on central phenyl ring draw particular interest as the variation in the location of spacer on the phenyl ring would result in a variety of molecular architectures, namely, star-like, bent-core, λ, and T-shaped mesogens. − Depending on the spacer length as well as the length of the rigid core, a wide range of mesophase morphologies like nematic, smectic, banana, and columnar phases have been realized. , In this scenario, it will be interesting to investigate mesogens containing five-membered heterocyclic systems in the spacer unit.…”