Two series of banana‐shaped liquid crystalline (LC) H‐bonded complexes HPm/CBn (i.e., bent‐core H‐bonded side‐chain homopolymer HP mixed with bent‐core covalent‐bonded small molecule CB) and CPm/HBn (i.e., bent‐core covalent‐bonded side‐chain homopolymer CP mixed with bent‐core H‐bonded small molecular complex HB) with various m/n molar ratios were developed. The bent‐core covalent‐ and H‐bonded structural moieties were homopolymerized in the banana‐shaped LC H‐bonded complexes HPm/CBn and CPm/HBn, respectively. The influences of m/n molar ratios (polymeric moieties vs. small molecular moieties) on the mesomorphic and electro‐optical properties of both banana‐shaped LC H‐bonded complexes HPm/CBn and CPm/HBn were investigated. The polar smectic phases could be achieved and stabilized by smaller contents of polymeric dopants in banana‐shaped LC H‐bonded complexes, such as HP1/CB10, HP1/CB15, CP1/HB10, and CP1/HB15, which possessed tunable spontaneous polarization (Ps) values according to the molar ratios of m/n, that is, lower Ps values obtained in H‐bonded complexes HPm /CBn and CPm / HBn with higher ratios of H‐bonded moieties (larger m/n molar ratios), respectively. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 764–774, 2010

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The stabilization of bend configuration in optical compensated bend (OCB) mode cells by doping bent-core molecules was developed in this study. The values of response time (τ) and threshold voltage (V th ) in OCB cells were dependent on not only the concentration but also the shape, dipole direction, and flexible chain length of the doping molecules. Experimental results showed that the total response time (τ total ) and threshold voltage (V th ) of OCB cells could be reduced by doping bent-core molecules, and smaller τ values by reducing flexible chain lengths as well as smaller V th values by reducing polarization of bent-core molecules were normally obtained. In general, higher concentrations of dopants normally induced shorter field-on response time (τ on ) and a minimum field-off response time (τ off ) occurred at 0.5% of doping concentration, where the fastest total response time (τ total ) values were achieved. IntroductionThe technologies of liquid crystal displays (LCDs) have been well developed in recent years. Optical compensated bend (OCB) mode liquid crystal displays (LCDs) were also expanded into LCD panels to have the advantages of fast response time (RT) and wide view angle. Bend state, which would be switched from fieldoff state of splay arrangement, is a useful working condition (field-on state) for OCB cells under electric fields. Therefore, suppression or elimination of splay state to reduce response time and operating voltage were also necessary for the improvement of OCB mode. Various techniques of using optical polymerization of UV curable liquid crystal (LC) monomers[1]-[3] were performed to generate polymer walls so as to stabilize bend alignment. In addition, nano-scaled dopants such as nanoparticles[4]-[7] or carbon nanotubes (CNT)[8] were deliberated to reduce the operating voltage and response time in twisted nematic (TN) mode cells. Moreover, polymer stabilized cholesteric texture cells with different chiral dopants and reactive monomers were investigated [6] to survey the effect of doping concentration.In this study, a new approach of utilizing bent-core dopants in OCB cells was developed. Novel bent-core materials with threearomatic ring structures containing polar ester linking groups and different flexible chain lengths (n = 3, 6, and 9) were synthesized (as shown in Fig. 1, where CB1-CB4 are bent-core dopants and CB5 is a linear-shape dopant) and doped into commercial nematic LC host (ZCE-5096) with various doping ratios (0, 0.1, 0.5, 1, and 5 wt%) as guest-host LC mixtures to be utilized in the OCB mode LCDs. The doping effect of bent-core materials on the electro-optical properties of these LC mixtures (LC host doped with different bent-core and linear-shaped materials) in OCB cells were surveyed. CB1: A = CB2: A = CB3: A = n = 3 n = 6 n = 12 CB4: A = CB5: A = N n = 6 n = 6 A O O O O OC n H 2n+1 H 2n+1 C n O Fig. 1 Molecular structures of bent-core (CB1-CB4) and linear-shaped (CB5) dopants. ExperimentalAll chemical structures of doping materials were well characterized by 1 H...

Mo (2010) Dopant effects of photoreactive ZnO nanoparticles on fast response LC materials in optical compensated bend (OCB) mode liquid crystal displays, ABSTRACTPhotoreactive ZnO nanoparticles containing surface-modified acrylate groups were synthesized and applied to improve the threshold voltage in optical compensated bend (OCB) mode liquid crystal display (LCD) cells. The dopant effects of ZnO nanoparticles with or without commercial reactive monomer additives (1 wt% doping ratio) on the values of threshold voltage (V th ) and response time in OCB cells were explored by applying different voltages to photo-reactive ZnO nanoparticles during UV curing processes in OCB cells to compare the influences of doped ZnO nanoparticles. As a result, we successfully eliminated or reduced the splay state of OCB mode and thus reduced threshold voltage. However, lower transmissions and higher values of the response time were observed in OCB cells doped with photoreactive ZnO nanoparticles, and the decreasing of V th is independent of various doping materials. Moreover, lower transmission and high response time could be improved through sequential voltage-applied procedures, i.e., bend black mode (10 V) → bend white mode (2.5 V), under the immobile minimum threshold voltage at the bent state during UV curing processes to achieve lower pre-transition and fast response time properties by only doping photoreactive ZnO nanoparticles.