Novel supramolecular side-chain banana-shaped liquid crystalline (LC) polymer complexes AmBn-N bearing various (m/n) molar ratios of hydrogen-and covalent-bonded bent-core components were acquired by the free radical polymerization, where the hydrogen-bonded (H-bonded) structures were executed via mixing equimolar portions of proton donor (H-donor) polymers AmBn (homopolymers/ copolymers) and pyridyl proton acceptor (H-acceptor) bent cores (small molecules). The influences of the molar ratios of bent-core H-bonded components in side-chain banana-shaped LC polymers and their corresponding polymer complexes on mesomorphic and electro-optical properties were first investigated. The voltage-dependent antiferroelectric properties of spontaneous polarization (Ps) values in the polar smectic phase of the supramolecular side-chain banana-shaped copolymers were also reported. The nematic and tilted smectic phases were verified by XRD measurements, and the SmCP phase was further confirmed by the triangular wave method. Surprisingly, a novel enantiotropic polar smectic (SmCP A ) phase was generated in some bent-core side-chain polymer complexes AmBn-N. Therefore, a special approach to constructing (or stabilizing) the SmCP phase was first developed in this study by copolymerization of bent-core covalent-and H-bonded units in side-chain polymer complexes (with proper m/n molar ratios of 16/1 and 10/1) from both bent-core covalent-and H-bonded monomers (i.e., B and A-N units, respectively) without the SmCP phase.
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.
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