Physical Properties of Main-Chain Liquid Crystalline Polyurethanes
碩士 === 元智大學 === 化學工程學系 === 91 === In this study, we report physical properties of main-chain liquid crystalline polyurethanes. Thermotropic hard segment type liquid crystalline polyurethanes can be obtained by a step polyaddition reaction from mesogenic diols with diisocyanates. All the t...
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| Format: | Others |
| Language: | zh-TW |
| Published: |
2003
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| Online Access: | http://ndltd.ncl.edu.tw/handle/99726372720964243800 |
| Summary: | 碩士 === 元智大學 === 化學工程學系 === 91 === In this study, we report physical properties of main-chain liquid crystalline polyurethanes. Thermotropic hard segment type liquid crystalline polyurethanes can be obtained by a step polyaddition reaction from mesogenic diols with diisocyanates. All the thermal decomposition behavior of polyurethanes are about 300℃. It shows that the technical application of polyurethanes is limited. In order to obtain polymers with a high application we became interested in the study of decrease of the hard segment melting points to enhance mesogenic temperature range △TLC (i.e. △TLC =Tm→TN-I). Phase segregation of polyurethanes was investigate by DSC, FTIR and POM. It was found that the temperatures of phase transitions depend on the amount of mesogenic diols substituted for 1,4-BD. They show a higher transition temperature (Tg and Tm) when the polyurethanes have been raised by the increase of the amount of mesogenic diols. The transition temperatures and the temperature ranges of mesophases also changed with the length of alkoxy spacer and the kind of diisocyanate. The longer the spacer length, the lower is the transition temperature. And MDIn shows a higher Td than that of TDIn.
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