Induction of the Columnar Phase of Unconventional Dendrimers by Breaking the C2 Symmetry of Molecules |
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| Authors: | Prof. Dr. Long‐Li Lai Sheng‐Wei Wang Dr. Kung‐Lung Cheng Dr. Jey‐Jau Lee Tsai‐Hui Wang Prof. Dr. Hsiu‐Fu Hsu |
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| Affiliation: | 1. Department of Applied Chemistry, National Chi Nan University, No. 1 University Rd., Puli, Nantou, Taiwan 545, Fax: (+886)?49‐2917956;2. Material and Chemical Research Laboratories, Industrial Research Institute, Hsinchu, Taiwan 300;3. No. 101 Hsin‐Ann Rd., HsinChu Science Park, Hsinchu, Taiwan 300;4. Department of Chemistry, Tamkang University, Tamsui, Taiwan 251 |
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| Abstract: | Two triazine‐based unconventional dendrimers were prepared and characterized by 1H and 13C NMR spectroscopy, mass spectrometry, and elemental analysis. Differential scanning calorimetry, polarizing microscopy, and powder XRD studies showed that these dendrimers display columnar liquid‐crystalline phases during thermal treatment. This is ascribable to breaking of their C2 symmetry. The molecular conformations of prepared dendrimers were obtained by computer simulation with the MM3 model of the CaChe program in the gas phase. The simulation showed that the conformations of the prepared dendrimers are rather flat and disfavor formation of the LC phase. However, due to C2‐symmetry breaking, the prepared dendrimers have structural isomers in the solid state and thus show the desired columnar phases. This new strategy should be applicable to other types of unconventional dendrimers with rigid frameworks. |
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| Keywords: | dendrimers liquid crystals nitrogen heterocycles symmetry breaking |
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