期刊
MACROMOLECULAR RESEARCH
卷 17, 期 12, 页码 976-986出版社
POLYMER SOC KOREA
DOI: 10.1007/BF03218645
关键词
aromatic polyimides; nanoscale thin films; liquid crystals; rubbing process; surface chain orientation; surface topography; microgrooves; anisotropic molecular interaction; liquid crystal orientation; optical retardation; azimuthal anchoring energy; polar anchoring energy
资金
- Korea Science & Engineering Foundation of the Ministry of Education, Science & Technology (NEST) of Korea
- MEST
- Ministry of Knowledge Economy of Korea [F0004011-2008-31]
With the study goal of firstly elucidating the anisotropic interactions between oriented polymer chain segments and liquid crystal (LC) molecules, and secondly of determining the contributions of the chemical components of the polymer segments to the film surface topography, LC alignment, pretilt, and anchoring energy, we synthesized three dianhydrides, 1,4-bis(4'-t-butylphenyl)pyromellitic dianhydride (BBPD), 1,4-bis(4'-trimethylsilylphenyl)pyromellitic dianhydride (BTPD), and 2,2'-bis(4 ''-tert-butylphenyl)-4,4',5,5'-biphenyltetracarboxylic dianhydride (BBBPAn), and a series of their organosoluble polyimides, BBPD-ODA, BBPD-NMA, BBPD-MDA, BTPD-FDA, and BBBPAn-FDA, which contain the diamines 4,4'-oxydianiline (ODA), 4,4'-methylenediamine (MDA), and 4,4'-(hexafluoroisopropylidene)dianiline (FDA). All the polyimides were determined to be positive birefringent polymers, regardless of the chemical components. Although all the rubbed polyimide films exhibited microgrooves which were created by rubbing process, the film surface topography varied depending on the polyimides. In all the rubbed films, the polymer chains were unidirectionally oriented along the rubbing direction. However, the degree of in-plane birefringence in the rubbed film varied depending on the polyimides. The rubbing-aligned polymer chains in the polyimide films effectively induced the alignment of nematic LCs along their orientation directors by anisotropic interactions between the preferentially oriented polymer chain segments and the LCs. The azimuthal and polar anchoring energies of the LCs ranged from 0.45x10(-4) - 1.37x10(-4) J/m(2) and from 0.86x10(-5) - 4.26x10(-5) J/m(2), respectively, depending on the polyimides. The pretilt angles of the LCs were in the range 0.10-0.62 degrees. In summary, the soluble aromatic polyimides, reported here are promising LC alignment layer candidates for the production of advanced LC display devices.
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