Papers by Author: Qing Lan Ma

Abstract: In the presence of the catalyst N, N-dimethylbenzylamine, a series of ultraviolet-curable sealants 1-6 were synthesized by varying the catalyst amount from 0.5, 1.0, 1.5, 2.0, 2.5 and 3.0 part in the process of polymerizing the epoxy resin (25 parts) with acrylic acid (17.5 parts). After having been cured by UV light, the transmittance of equally-thick films of the sealants changed with the amount of the catalyst. Furthermore, we recorded the transmittance of UV-cured sealant films when aged in air at high temperatures. Our results have demonstrated that the amount of catalyst poses limited effects on the transmittance of the synthesized sealants

Abstract: Ultraviolet curable sealant was synthesized by polymerizing epoxy resin with acrylic acid in the presence of catalyst N,N-dimethylbenzylamine. The synthesized ultraviolet-curable sealant could be solidified upon exposure to 365 nm ultraviolet irradiation for 8 seconds. The optical, mechanical and thermal properties of the ultraviolet-cured sealant were investigated with ultraviolet-visible spectrometer, tensile machine and differential scanning calorimetry, respectively. Our results demonstrated that the transparent and thermally stable sealant was strong enough for liquid crystal display panels.

Abstract: The effects of cyclic heating and cooling on the banana-phase growth behaviors of the prototype banana-shaped liquid crystal 1,3-phenylene-bis[4-(4-octylphenylimino)methyl]benzoate were investigated with differential scanning calorimetry and polarized optical microscopy, respectively. Cyclic heating and cooling can reduce the phase transition temperatures and increase the domain sizes of the banana phases of the banana-shaped liquid crystal. These results can be interpreted in terms of the nucleation and growth of the banana phases out of its isotropic phase of the banana-shaped liquid crystal.

Abstract: We demonstrate that a bent-core liquid crystal 1,3-phenylene-bis(4-butoxybenzylidene amine) can write the Chinese character 人, which means a person in English, when the bent-core compound gets cooled from its isotropic phase. The polarized optical microscopic graphs illustrate that the bent-core molecules are able to self-assemble themselves into the Chinese character either in a sequential order or in a reverse order. Our results reveal that bent-core molecules have the capability of being smart materials.

Abstract: . We demonstrate that banana-shaped molecules 1,3-phenylene bis(4-methoxybenzylidene amine) can assemble themselves into diffraction gratings when the melt of the banana-shaped compound, which was sandwiched between two pieces of glass substrates, is cooled to room temperature. Polarizing optical microscopic characterization shows that a pattern of periodic modulation of the refractive index can be developed in the thin films formed by the banana-shaped compound. Despite the gratings are groove free, their optical properties are the same as classically ruled gratings. Our work provides an alternative method for manufacturing diffraction gratings by harnessing the self-assembly of banana-shaped molecules.

Abstract: The influence of cooling rate on the phase transitions of a three-benzene-ring containing bent-core liquid crystal 1,3-phenylene-bis[4-(hexylcarboyloxyl)benzylideneamine] has been investigated by means of differential scanning calorimetry and polarized optical microscopy. Our results show that the cooling rates in the second cooling run pose significant effects on the phase transitions of the bent-core liquid crystal despite the cooling rates in the first cooling run pose little effects on the phase transitions. In the second cooling run, the banana phases survived only when the cooling rates were in the range of 14~15oC/min whereas both slow cooling rates which were less than 13oC/min and fast cooling rates which were higher than 16oC/min made the banana phases disappeared.

Abstract: Periodically birefringent thin films growing out of the isotropic phase of the banana-shaped liquid crystal 1,3-phenylene-bis (4-butoxybenzyldiamine) were investigated with polarized optical microscopy. The gown thin films of the periodic modulation of the birefringent index self-assembled by the banana-shaped LC molecules were attributed to the difference of the molecular composing structures. Further the driving forces of the banana-shaped molecular self-assembly were discussed.

Abstract: A cholesteric liquid crystal cholesteryl nonanoate was synthesized and then characterized by means of differential scanning calorimetry and polarized optical microscopy. As temperature decreased from its clearing point, cholesteric phase was formed for cholesteryl nonanoate and accompanied by continuous evolution of colors in the focal conic textures. Furthermore, beautiful spherulite crystals were observed to grow out of the cholesteric phase as the crystallization continued. The evolution of the colors in recorded textures was contributed to temperature-dependent selective reflection of the liquid crystal.

Abstract: A bent-core compound with three benzene-ring cores 1,3-phenylene-bis [4-(nonylcarboyloxyl)benzyl ideneamine] was synthesized. Its mesomorphic properties were characterized with differential scanning calorimetry and polarized optical microscopy, respectively. This kind of bent-core compound exhibited mesophases in the temperature range of 155-185oC for the first cooling but cyclic heating and cooling could lower the phase transition temperatures for this bent-core liquid crystal. Our results demonstrated that bent-core molecules with three benzene-ring cores can also form mesophases as those five benzene-ring containing bent-core molecules do.

Abstract: A homologous series of three-benzene-ring containing bent-cores compounds 1,3-phenylene-bis[4-(alkylcarboyloxyl)benzylideneamine] were synthesized. In these molecules the terminal ester chains CH3(CH2)n-2COO-, where n was the number of carbon atoms in the terminal chains, were linked to the central three-benzene-ring containing bent-core. As n changed from 1-12, the melting temperatures and clearing points were in the high temperature ranges of 136-206oC. As n changed in the range of 14-19, the melting temperatures and clearing points were dramatically dropped in a low temperature ranges 60-82oC.