Configuration Effects of H-Bonded Sites and Rigid Core Lengths on H-Bonded Banana-Shaped Liquid Crystalline Supramolecules Consisting of Symmetric Trimers and Asymmetric Heterodimers

Abstract

Several series of novel banana-shaped H-bonded symmetric trimers (with two H-bonds) and asymmetric heterodimers (with one H-bond) were self-assembled by appropriate molar ratios of proton donors (H-donors) and acceptors (H-acceptors). The influences of H-bonded linking positions and aromatic ring numbers (4-8 aromatic rings in the rigid cores) as well as the chain lengths (n, m = 12 or 16, respectively, in the flexible parts) on the mesomorphism and the switching behavior of the bent-core supramolecules were evaluated and theoretically analyzed. Except for the supramolecular structures with longer rigid cores or shorter flexible chains possessing the rectangular columnar (Col(r) or B1) phase, the SmC(A)P(A) phase was revealed in most supramolecular asymmetric heterodimers and switched to the SmC(S)P(F) phase by applying electric fields. The polar smectic C phase was dominated for those with H-bonded sites apart from the core center. Interestingly, the SmA and nematic phases were observed in H-bonded asymmetric dimers with H-bonded sites close to the core center, which theoretically proved that the polar smectic C phase was disfavored due to an unfavorable bend angle (smaller than the lower limit of 110 degrees ) in the lowest-energy H-bonded conformer. Compared with the fully covalently bonded analogue, lower transition temperatures and lower threshold voltages were developed in the H-bonded asymmetric dimers with the polar smectic C phase. On the basis of the theoretical calculations of molecular modeling, the existence of polar switching behavior in the polar smectic C phase of asymmetric heterodimers was proven to be associated with their configurations with higher dipole moments and suitable bend angles. Furthermore, the lack of polar switching behavior in supramolecular symmetric trimers, which exhibited the regular SmC phase with weak electrical stabilities, was related to their configurations with smaller dipole moments and confirmed by theoretical calculations.

Polymeric dopant effects of bent‐core covalent‐bonded and hydrogen‐bonded structures on banana‐shaped liquid crystalline complexes

“…As shown in Figure 7(b), the P s values of 280 and 450 nC/cm 2 were saturated at high voltages ( V pp > 200 V) for H‐bonded complexes HP1/CB10 and HP1/CB15 , respectively. Compared with H‐bonded complexes, the saturated P s value of 500 nC/cm 2 in CB (the bent‐core covalent‐bonded small molecule) was obtained at a much higher voltage above V pp = 320 V in our previous study 24. This might be explained by that the host system of covalent‐bonded molecule CB doped with H‐bonded polymer HP would reach saturated P s values at lower voltages due to the softer bent‐core mixed configurations in H‐bonded complexes HP1/CB10 and HP1/CB15 .…”

“…Interestingly, the switching current behavior of the SmCP phase in the monomeric units was sustained and the ferro‐electricity could be modified by the polymer structural design of dimethylsiloxane diluted polysiloxane side‐chain copolymer frameworks 13. According to the previous works, bent‐core H‐bonded small molecules could yield lower mesophasic transition temperatures, enthalpies, and threshold voltages than those of fully covalent‐bonded five‐ring banana‐shaped molecular analogues and H‐bonded side‐chain polymeric derivatives, which suggested that softer bent‐core intermolecular arrangements were present in both H‐bonded and small molecular designs 22–24. Regarding the small molecular systems containing two different fully covalent‐bonded components, unusual molecular arrangements and mesomorphic behaviors were developed by blending rod‐like liquid crystals with bent‐core LC dopants 25, 26.…”

Self-assembled 1,2-bis[4-(4-(10-decyloxy)phenylazo)]benzoylhydrazine dimer and its hydrogen-bonded complexes

“…The XRD pattern (1D and 2D) was shown in Figure 8(a),(b) (at 1408C upon cooling). The molecular arrangement of the rectangular columnar phase in complex 4j is depicted in Figure 8(c) of which the d1 ¼ 4.36 nm (2u ¼ 1.88) and d2 ¼ 3.41 nm (2u ¼ 2.218) are the long and short axes of Col r phase, respectively, and l ¼ 0.5 nm (2u ¼ 15.48) is the lateral molecular distance (11,18). The present complex 4j that possesses four azo linkages favours the disc-shaped arrangement as that reported for nicotinic acid derivatives (19).…”

Bent-core 6-thioxoverdazyl: a comparison of mesogenic properties with the 6-oxo analogue

“…Benzaldehyde 4-benzoyloxyphenylhydrazone (4) and 1,5-bis(4-hydroxyphenyl)-3-phenyl-6-oxoverdazyl were prepared following literature protocols. [16] Acyl chloride 9 [16] was prepared from corresponding carboxylic acid [19] by treatment with a slight excess SOCl 2 in dry CH 2 Cl 2 in the presence of catalytic amounts of dry DMF.…”