Recently the β relaxation draws attention because it may act as a precursor of the α relaxation and potentially influences a wide range of properties. In many cases, the weak intensity of the β relaxation limits the experimental investigation. Herein, the β relaxation of poly(diethyl fumarate) (PDEF) using differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and dielectric spectroscopy is investigated. Originating from the absence of methylene spacer in the main chain, polyfumarates possess an intense β relaxation. Unlike common vinyl polymers, PDEF shows two distinct steps in DSC measurement corresponding to α and β relaxations. Interestingly, the relative intensities of α and β relaxations depend on the thermal history. The β relaxation of PDEF obtained by dielectric spectroscopy at high temperature is similar to that of poly(methyl methacrylate) (PMMA). However, the β relaxation of PDEF follows the VFT equation rather than the Arrhenius equation at low temperatures. The analysis of PDEF/PMMA blend suggests the local orientation of PDEF chain plays a vital role in the intense β relaxation.

中文翻译：

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聚富马酸二乙酯作为聚（取代亚甲基）的 α 和 β 弛豫特性

最近β弛豫引起了人们的注意，因为它可能作为α弛豫的前体并可能影响广泛的性质。在许多情况下，β弛豫的弱强度限制了实验研究。在此，使用差示扫描量热法 (DSC)、动态力学分析 (DMA) 和介电光谱研究了聚富马酸二乙酯 (PDEF)的β弛豫。由于主链中不存在亚甲基间隔基，聚富马酸酯具有强烈的β弛豫。与常见的乙烯基聚合物不同，PDEF 在 DSC 测量中显示出两个不同的步骤，分别对应于α和β放松。有趣的是，α和β弛豫的相对强度取决于热历史。在高温下通过介电光谱获得的 PDEF的β弛豫与聚（甲基丙烯酸甲酯）（PMMA）的相似。然而，PDEF的β弛豫遵循 VFT 方程而不是低温下的 Arrhenius 方程。对 PDEF/PMMA 混合物的分析表明 PDEF 链的局部取向在强烈的β松弛中起着至关重要的作用。