淡江大學機構典藏:Item 987654321/44150
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    题名: Analysis of rapid chain dynamics in isochronal dielectric measurements of polymers
    作者: Yang, Yuning;賴偉淇;Lai, Wei-chi;Hsu, Shaw-ling
    贡献者: 淡江大學化學工程與材料工程學系
    日期: 2007-08-03
    上传时间: 2010-03-09 09:57:50 (UTC+8)
    出版者: Melville: American Institute of Physics (AIP)
    摘要: Fast dynamics within the microwave frequency range (approximately gigahertz) in polymer systems as a function of temperature (in the range from 20 to 190 °C) were studied using high frequency dielectric spectroscopy. The frequency of radiation was varied from 0.5 to 18 GHz. The isochronal dielectric loss data were taken to eliminate the complexity arising from the frequency-independent, temperature-dependent background loss in the condensed phase. These studies were conducted for poly(caprolactone) (PCL), poly(ethylene oxide) (PEO), poly(ethylene oxide) with methoxy end group (PEO-CH3), PLA-b-PEO-b-PLA triblock copolymers, and several polymers with high glass transition temperatures. These polymers possess glass temperatures ranging from −62 °C (PCL) to 110 °C (PMMA). One broad relaxation process was found only for polymers (PCL, PEO, and PLA-b-PEO-b-PLA) with low glass transition temperatures. The effect due to end groups was investigated by comparing the results of PEO with hydroxy versus methoxy end groups. The measured relaxation process was determined not to be associated with end groups. The results from temperature-dependent dielectric spectroscopy indicate that the relaxation process follows an Arrhenius T dependence suggesting that it is due to local motions. The activation energy of the relaxation process was measured and investigated based on the coupling model. The results suggest that the observed relaxation process behaves as a Johari-Goldstein β relaxation.
    關聯: Journal of Chemical Physics 127(5), pp.054901
    DOI: 10.1063/1.2756036
    显示于类别:[化學工程與材料工程學系暨研究所] 期刊論文

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