A Small Change in Central Linker Has a Profound Effect in Inducing Columnar Phases of Triazine‐Based Unconventional Dendrimers |
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| Authors: | Prof Dr Long‐Li Lai Jei‐Way Hsieh Dr Kung‐Lung Cheng Shih‐Hsien Liu Dr Jey‐Jau Lee Prof Dr Hsiu‐Fu Hsu |
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| Institution: | 1. Department of Applied Chemistry, National Chi Nan University, No.?1 University Rd., Puli, Nantou 545 (Taiwan), Fax: (+886)?49‐2917956;2. Material and Chemical Research Laboratories, Industrial Research Institute, Hsinchu 300 (Taiwan);3. No.?101 Hsin‐Ann Rd., HsinChu Science Park, Hsinchu 300 (Taiwan);4. Department of Chemistry, Tamkang University, Tamsui 251 (Taiwan) |
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| Abstract: | Four unconventional triazine‐based dendrimers have been prepared and characterized by 1H and 13C NMR spectroscopies, mass spectrometry, and elemental analysis. Based on DSC studies, polarizing microscopy, and powder XRD, two of these dendrimers, containing linkers with an odd number of carbon atoms, were observed to display columnar liquid–crystalline phases during thermal treatment. However, the other two dendritic analogues, containing linkers with an even number of carbon atoms, were not observed to behave correspondingly. Based on computer simulation, we reasonably assume that the dendrimers with an odd number of carbon atoms in their linkers distort their molecular shape and adopt two isomeric structures due to asymmetrical congestion. This reduces the molecular π–π face‐to‐face interaction, which in turn causes the dendrimers to form columnar LC phases during thermal treatment. However, the dendrimers with an even number of carbon atoms in their linkers have more symmetrical skeletons and do not display any liquid–crystalline phase upon thermal treatment. This new strategy should be applicable for eliciting the columnar liquid–crystalline properties of other types of unconventional dendrimers with rigid frameworks. |
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| Keywords: | asymmetrical congestion columnar phases dendrimers mesophases triazines |
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