Control of Molecular Aggregations by Doping in Mesophases:  Transformation of Smectic C Phases to Smectic C_A Phases by Addition of Long Bent-Core Molecules Possessing a Central Strong Dipole

Abstract

Compounds 1 − 3, each possessing a long bent-rod shape and a central large dipole, were designed and synthesized as dopants which transform liquid-crystal smectic C phases to smectic CA phases. The properties and the layer structures of the dopant molecules in the mesophases were investigated by polarized light microscopy, differential scanning calorimetry (DSC), and X-ray diffraction (XRD). Induction of smectic CA phases from the smectic C phases of compounds 4 − 7 was performed by doping with a small amount of dopants 1 − 3. In particular, even 1 wt % (0.5 mol %) of 3c was enough to convert the Sm-C phase into the Sm-C A phase in the case of 4. In addition, matching in the core-lengths was important for the induction. Further, importance of the central dipole was also confirmed by replacement of the CF3 groups of compound 1 with CH3 or H.

A bent‐core dopant‐induced smectic A* twist state†

“…The latter have lately attracted considerable interest due to their polar properties arising from achiral molecules [22], but only few reports towards their use as dopant molecules have been published to date. These have shown induced antiferroelectric phases in ferroelectric hosts [23,24] and enhanced chirality by addition of achiral bent-core molecules to chiral hosts [25][26][27].…”

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

“…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. Meanwhile, the blended polymeric systems (mainly side‐chain polymers) were expanded by doping,27 copolymerization,28–33 and H‐bonded complexation34 with chiral/achiral LC components to induce the particular mesomorphic and electro‐optical properties.…”

Thermoluminescence measurements of liquid crystal azomethines and poly(azomethines) with different shapes as thermo-detectors

“…Obtained azomethines and poly(azomethines), depending on the chemical structure, emitted mainly blue or green light [1][2][3][4][5][6][7][8][9]. In addition, small compounds and polymers with imine bond are investigated as liquid crystal materials with bent (banana) [10][11][12][13][14] or rod [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32] shape. Depending on the chemical structure the investigated compounds exhibited one mesophase or rich polymorphism 34,35].…”