Glass transition of polymer-molecular liquid mixtures studied by broadband dielectric spectroscopy

为了研究聚合物和分子液体在聚合物溶液中的动力学行为，在30 GHz - 1μ Hz频率范围内测量了极性聚合物和溶剂混合物的宽带介电谱。聚乙烯吡咯烷酮（PVP）-醇混合物的介电弛豫在25℃下，对聚乙烯吡咯烷酮（PVP）-醇与单羟基和多羟基醇的混合物进行了BDS测量。在2 GHz - 100 MHz和10 MHz - 10 kHz频率范围内，分别观察到由醇分子运动和PVP分子链局部运动引起的介电弛豫过程。一元醇的弛豫时间由氢键密度ρ_（？<HB>）另一方面，多羟基醇的弛豫时间不是由ρ_决定的<HB>。这些结果表明，决定单羟基醇弛豫时间的机理与多羟基醇不同。PVP的弛豫时间随着PVP浓度的增加而增加，因为聚合物链之间的相互作用的增加使弛豫时间变大。PVP无限稀释时的弛豫时间与多元醇的粘度成正比，与一元醇的1.3次方成正比。在128 - 298 K的温度范围内，在10 mHz - 10 GHz的频率范围内，对65wt%的乙二醇低聚物（EGO）-水混合物的各种EGO重复单元进行了BDS测量。根据这些实验结果，在液态下观察到的介电损耗峰的形状与水和EGO分子之间的协同性以及在接近玻璃化转变温度的低温范围内α-和β-过程的分离情况有关。

In order to make clear the dynamics of polymer and molecular liquid in polymer solutions, broadband dielectric spectroscopy of the mixtures with polar polymer and solvent were measured in the frequency range of 30 GHz - 1μHz.1. Dielectric relaxation of PVP-alcohol mixturesBDS measurements were carried out for poly(vinyl pyrrolidone)(PVP)-alcohol mixtures with mono- and poly-hydroxyl alcohols at 25℃. The dielectric relaxation processes due to the molecular motions of alcohol and local chain motion PVP were observed in the frequency ranges of 2 GHz - 100 MHz and 10 MHz - 10 kHz, respectively. The relaxation times of mono-hydroxyl alcohols were determined by the density of hydrogen-bond, ρ_<HB>. On the other hand, the relaxation times of poly-hydroxyl alcohols were not determined by ρ_<HB>. These results imply that the mechanism which determines the relaxation time of mono-hydroxyl alcohols is different from that of the poly-hydroxyl alcohols. The relaxation time of PVP increases with the PVP concentration, since the increase of the interactions among the polymer chain makes the relaxation time larger. The relaxation time at the infinite dilution of PVP is proportional to the viscosity of poly-alcohol and proportional to 1.3 powers of that of mono-alcohols.2. Dielectric relaxation of EGO-water mixtures on liquid to glassBDS measurements of 65 wt% ethylene glycol oligomer (EGO)-water mixtures for various repeat units of EGO were carried out in the frequency range of 10 mHz - 10 GHz in the temperature range of 128 - 298K. According to these experimental results, the shape of dielectric loss peak observed in the liquid state is related to the cooperativity between water and EGO molecules and the separation scenario of the α- and β-processes in low temperature range close to the glass transition temperature.