Relaxation processes in hyperbranched polyesters
Relaxation processes in hyperbranched polyesters
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超支化聚酯的松弛过程
DOI：
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发表时间：
1994
期刊：
影响因子：
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通讯作者：
U. Gedde
中科院分区：
文献类型：
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作者：
E. Malmström;F. Liu;R. H. Boyd;A. Hult;U. Gedde
在100K至350K之间，测量了两种超支化聚酯、一种五代羟基官能化聚合物(5G-OH)和一种三代端烷基聚合物(3G)各50/50混合物的样品在100K到350K之间的10-2 Hz-10 kHz范围内的介电常数和损耗。用差示扫描量热法研究了超支化聚合物的热转变。在5G-OH：α中发现了三个弛豫转变，玻璃化-橡胶转变和两个亚玻璃化过程β和γ均表现出阿累尼乌斯温度依赖性，其活化能均为96±2kJmol-1。低温过程可以归结为末端羟基的运动，而β是由于酯基的重新定向。样品3G显示只有一个玻璃化转变和一个亚玻璃化过程被分配给酯基的重新定向。该过程的高活化能(202kJ·mol-1)表明，该聚合物中的酯基被高度限制。
SummaryDielectric permittivity and loss have been measured over the frequency range 10-2 Hz-10 kHz between 100 K and 350 K for samples of 50/50 mixtures of each of two hyperbranched polyesters, one five-generation hydroxy functional (5G-OH) and one threegeneration alkyl-terminated polymer (3G), with dielectrically inactive linear polyethylene. The thermal transitions of the hyperbranched polymers were studied with differential scanning calorimetry. Three relaxation transitions were found in 5G-OH: α, the glass-rubber transition and two subglass processes denoted β and γ showing Arrhenius temperature dependence both with an activation energy of 96±2kJ mol-1. The low temperature process could be assigned to motions of the terminal hydroxyl groups whereas β is due to reorientation of the ester groups. Sample 3G showed only a glass transition and one subglass process being assigned to reorientation of the ester groups. The high activation energy (202 kJ mol-1) of this process indicates that the ester groups are highly constrained in this polymer.