Effect of molecular weight on two smectic polyesters |
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Authors: | Hong-Bing Tsai Da-Kong Lee Hsien-Wen Chen Jia-Yeh Chang Jung-Liang Liu Chih-Huey Chang I-Chung Du Sheng-Yuan Lei Jiang-Wen You |
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Affiliation: | (1) Department of Chemical Engineering, National I-Lan Institute of Agriculture and Technology, 26015 I-Lan, Taiwan, Republic of China;(2) Ta Hwa College of Technology and Commerce, Chung-Lin, Hsin-Chu, Taiwan, Republic of China |
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Abstract: | The liquid crystalline transitions of two kinds of smectic polyesters with different molecular weights were investigated by DSC, polarized microscopy and X-ray diffraction. The molecular weight affects the transitions significantly for these two kinds of polyesters. With a high enough molecular weight, both poly (pentamethylenep,p -bibenzoate) and poly(hexamethylenep,p -bibenzoate) exhibit an enantiotropic smectic phase, but the two endothermic transition peaks of the DSC heating curve seem to overlap. The polyesters tend to exhibit a monotropic smectic phase as the molecular weight decreases. From the DSC cooling curve, the isotropic-smectic transition can be seen more clearly. As the molecular weight decreases, the smectic order decrease significantly. The molecular weight affects the transitions in a different way for these two different kinds of polyesters. |
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Keywords: | Thermotropic Liquid crystalline polymers Smectic Intrinsic viscosity Thermal transitions |
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