Influence of change in ether structure on the low temperature dielectric relaxation of some poly(ether imide)
Influence of change in ether structure on the low temperature dielectric relaxation of some poly(ether imide)
复制标题
醚结构变化对某些聚醚酰亚胺低温介电弛豫的影响
DOI：
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发表时间：
2014
期刊：
影响因子：
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通讯作者：
F. Santamaria
中科院分区：
文献类型：
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作者：
G. Eastmond;J. Paprotny;R. Pethrick;F. Santamaria
本文报道了一系列聚醚酰亚胺的宽频带介电弛豫谱。在结构上的变化允许的空间位阻约束的聚合物链的局部构象动力学的影响进行探讨。这些变化对这些聚合物的玻璃化转变温度具有显著影响，其范围为245至超过420°C。与此相反，这些聚合物的低温介电弛豫行为是非常相似的，是由于合作的本地的电致伸缩-librational运动。立体化学的变化影响弛豫过程的振幅、活化能、堆积链密度和高频极限介电常数e∞′的值。后一个参数对偶极诱导偶极和π-π电子相互作用的程度敏感，并且受堆积密度的影响。e∞′的大小是决定聚酰亚胺在电气应用中的适用性的一个非常重要的参数。e∞′的大小随密度的增加而增加;然而，当大的非极性基团抑制相邻链的相互作用时，观察到偏离这一总趋势。© 2014 Wiley Periodicals，Inc. J.应用聚合物Sci. 2014，131，41191。
Broad band dielectric relaxation spectra are reported on a range of polymers created by varying the ether segment in a series of poly(ether imide)s. Changes in the structure allow the effects of steric constraints on the local conformational dynamics of the polymer chain to be explored. These changes have a significant effect on the glass transition temperatures of these polymers which range from 245 to over 420°C. In contrast, the low temperature dielectric relaxation behavior of these polymers is very similar and is attributed to cooperative local oscillatory—librational motions. Changes in the stereochemistry effect the amplitude, activation energy for the relaxation process, the packing chain density, and values of the high frequency limiting permittivity, e∞′. This latter parameter is sensitive to the extent of dipole induced dipole and π-π electron interactions and is influenced by the packing density. The magnitude of e∞′ is a very important parameter in determining the suitability of poly(imide)s for electrical applications. The magnitude of e∞′ increases with the density; however, deviations from this general trend are observed when large nonpolar groups inhibit the interaction of neighboring chains. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 41191.