Abstract

In Part I of these 2 parts article, we derived mathematically the existence of a unique state for polymeric melts, occurring at a specific temperature above T_g, which we recognized to be the liquid–liquid transition, T_LL, observed and described by Boyer and others. T_LL is the temperature at which the melt is in an iso-free-volume and iso-enthalpic state independent of the molecular weight. It is a fundamental property of the material. The purpose of part II is to examine and explain the following: 1) the elusive character of T_LL (at the origin of the controversy about the existence of T_LL in the past), 2) the increase of free volume at T_LL, and 3) the endothermal change of heat capacity on heating across T_LL. Finally, our objective is to provide an explanation of T_LL and emphasize its importance as an example of a self-dissipative dynamic process that converts, at T_LL, into a classical thermally activated process. In this article, the experimental evidence found in the literature for T_LL is critically examined to point out the often biased reviews offered by the antagonistic authors of a controversy, here the pros and cons T_LL. We propose a Dual-Phase origin of the interactions in polymers to explain the weak and elusive manifestations of T_LL and show, by DSC, that the T_LL manifestations are made much more visible and prominent when the samples’ state has been brought out of equilibrium. We analyze, in detail, the thermally activated depolarization of samples which have been submitted to a polarization stage by a voltage field. The experimental technique of thermal stimulated depolarization (TSD), and its sister derivative the thermal windowing deconvolution (TWD), are unique and powerful analytical tools that can experimentally characterize “interactive coupling”, the factor that we have assumed is quantitatively responsible for the behavior of polymers and in particular of T_LL. The existence and the characteristics of T_LL were understood and predicted in Part I from rheological results by the use of the Thermo–Vogel–Fulcher equation whose thermo-kinetic terms, ΔH, ΔS, and T_∞, could be interpreted by the interactive coupling of the local free volume and the rotational isomeric conformational state of dual-conformers belonging to the macromolecules, themselves embedded in a collective dissipative system of interactions. The statistics controlling the interactive coupling parameters was described by the Dual-Phase and Cross-Dual-Phase models. In Part II, the same models are used to explain the interactive coupling manifestations specific to the TSD and TWD results. We show that certain characteristics of the TSD and TWD results are directly related to specific parameters of the Dual-Phase model. It is the case for the transitions visible by TSD, such as T_g,ρ related to space charges and local free volume (F-conformers), and T_LL marking the end of the specific impact of the Dual-Phase statistics on the properties. It is also the case when interactive coupling is analyzed by TWD: the compensation of the enthalpy and entropy of activation of the relaxations taking place at various polarization temperatures only occurs below T_LL, permitting its specific determination. We conclude pointing out the perhaps crucial importance of T_LL in establishing the distinct role of thermal energy in structuring or modulating the dynamics of the interactions. The Dual-Phase view of the interactions in polymers suggests that the local density difference between the b-grains and the F-conformers is “time-averaged” by the constant wiping (above T_g) of an “elastic dissipative wave” having a frequency, ω_o, i.e., a function of temperature and molecular weight, and thus is different from the Brownian dissipation, i.e., the thermal fluctuation characteristic of the Boltzmann’s mean field (the classical kT/h term). The elastic dissipative wave kinetically loses its collective modulation role and becomes the thermal wave at T_LL.

摘要

在这两部分文章的第一部分中，我们从数学上推导出了聚合物熔体的独特状态的存在，该状态发生在高于 T _g的特定温度，我们认为这是液-液转变 T _LL，由 Boyer 观察和描述和别的。T _LL是熔体处于等自由体积和等焓状态时的温度，与分子量无关。它是材料的基本属性。的第二部分的目的是为了检查和解释如下：1）T的难以捉摸的字符_LL（在约T的存在争论的来源_LL过去），2）的自由体积的在T的增加_LL, 和 3) T _LL加热时热容量的吸热变化。最后，我们的目标是解释 T _LL并强调其作为自耗散动态过程示例的重要性，该过程在 T _LL转换为经典的热激活过程。在本文中，对 T _LL文献中发现的实验证据进行了批判性审查，以指出争议的敌对作者提供的经常有偏见的评论，这里是利弊 T _LL。我们提出聚合物中相互作用的双相起源来解释 T _LL的微弱和难以捉摸的表现，并通过 DSC 表明 T _LL当样品的状态脱离平衡时，表现会变得更加明显和突出。我们详细分析了通过电压场进入极化阶段的样品的热激活去极化。热刺激去极化 (TSD) 的实验技术及其姊妹衍生品热窗口解卷积 (TWD) 是独特而强大的分析工具，可以通过实验表征“交互耦合”，我们假设的因素在数量上对行为负责聚合物，尤其是 T _LL。的存在和T的特性_LL在第一部分中，通过使用 Thermo-Vogel-Fulcher 方程（其热动力学项 ΔH、ΔS 和 T _∞）从流变学结果中理解和预测，可以通过局部自由体积和属于大分子的双构象体的旋转异构构象状态的相互作用耦合来解释，它们本身嵌入在相互作用的集体耗散系统中。控制交互耦合参数的统计数据由双相和交叉双相模型描述。在第二部分中，相同的模型用于解释特定于 TSD 和 TWD 结果的交互耦合表现。我们表明 TSD 和 TWD 结果的某些特征与双相模型的特定参数直接相关。TSD 可见的跃迁就是这种情况，例如与空间电荷和局部自由体积（F-conformers）相关的T _g,ρ和 T _LL标志着双相统计对属性的具体影响结束。TWD 分析交互耦合时也是如此：在不同极化温度下发生的弛豫的焓和熵的补偿仅发生在 T _LL以下，允许其具体确定。我们总结指出 T _LL在建立热能在构建或调节相互作用动力学方面的独特作用方面可能至关重要。聚合物中相互作用的双相视图表明 b 晶粒和 F 构象体之间的局部密度差异是通过“弹性耗散波”的恒定擦拭（高于 T _g）“时间平均”的，具有频率，ω_o，即温度和分子量的函数，因此不同于布朗耗散，即玻尔兹曼平均场的热波动特性（经典的 kT/h 项）。弹性耗散波在动力学上失去其集体调制作用，并在 T _LL成为热波。