Unsymmetrical trimesogens exhibiting the undulated twist grain boundary (UTGBC*) mesophase

Design and Synthesis of Chiral Nematic Liquid Crystals

“…Many other unsymmetrical dimers have also been based on Schiff's bases (143) [190][191][192], chalcones (144) [193], and tolane systems (145)(146)(147) [194,195]; these have all shown the formation of chiral nematic phases, but frequently show unusual phase behavior demonstrating the higher form chirality of the system, for example, BPs and TGB phases. Examples of these types of compounds are shown overleaf.…”

“…Although these materials have largely been supplanted as thermochromic materials, occasionally find application to conveniently impart chirality to a mesophase [47,180,186,[190][191][192][193][194][195]. …”

“…The (R,R)-and (S,R)-diastereoisomers may both be obtained as either the thermodynamic or the kinetic product of the reaction process. The final step involves the stereoselective thermal elimination of the sulfoxide group to give the (S)-cyclohexylidene ethanone (194) from the (R,R)-sulfoxide or the opposite enantiomer from the (S,R)-sulfoxides. Of the seven optically active cyclohexylidene ethanones synthesized, only three showed chiral nematic phases; these materials are listed in Table 14.9.…”

Synthesis and thermal properties of liquid crystal trimers comprising cyanobiphenyl and salicylaldimine anisometric segments

“…7 Thus far, three obvious kinds of trimers viz., symmetric 13,18,23 dwhere all the constituent mesogenic (A-A-A) units are identical, mixed 11,12,[14][15][16][17]21,22,[24][25][26][27] dtwo of the mesogens (A-B-A) are identical, and nonsymmetric 19,20 dnone of the mesogenic (A-B-C) units are identical, have been prepared and characterized. Seemingly, the mixed trimers, including supramolecular 28,29 systems (where the mesogenic segments are formed/ linked through the hydrogen-bond interactions) and metal-containing ones, 21 are reported in large numbers.…”

“…Liquid crystalline linear trimers (also referred to as trimesogens or triplet LCs), 7,[11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27] wherein three rod-like mesogenic entities are tide terminally through two flexible spacers, are considered as an important class of oligomers not only because of their interesting thermal behavior but also they help in studying how the LC behavior evolves from dimers to polymers. 7 Thus far, three obvious kinds of trimers viz., symmetric 13,18,23 dwhere all the constituent mesogenic (A-A-A) units are identical, mixed 11,12,[14][15][16][17]21,22,[24][25][26][27] dtwo of the mesogens (A-B-A) are identical, and nonsymmetric 19,20 dnone of the mesogenic (A-B-C) units are identical, have been prepared and characterized.…”