ALIPHATIC POLYESTERS AS MODELS FOR RELAXATION PROCESSES IN CRYSTALLINE POLYMERS .2. DIELECTRIC-RELAXATION IN COPOLYMERS OF ADIPIC ACID WITH 1,6 AND 2,5-HEXANEDIOLS
ALIPHATIC POLYESTERS AS MODELS FOR RELAXATION PROCESSES IN CRYSTALLINE POLYMERS .2. DIELECTRIC-RELAXATION IN COPOLYMERS OF ADIPIC ACID WITH 1,6 AND 2,5-HEXANEDIOLS
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DOI：
10.1016/0032-3861(84)90285-4
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发表时间：
1984-01-01
期刊：
影响因子：
4.6
通讯作者：
AYLWIN, PA
中科院分区：
文献类型：
--
作者：
BOYD, RH;AYLWIN, PA
线性脂肪族聚酯是研究结晶聚合物弛豫过程的有趣模型系统，因为它们以突出的方式显示γ和β弛豫，而在许多高度结晶的线性聚合物（LPE，POM等）中，β过程被抑制，并且与也具有显著β过程的支化聚乙烯不同，聚酯没有由于支化而引起的化学结构复杂化。为了研究β的外观变化（玻璃-橡胶）弛豫是由于结晶相的存在对无定形部分中长程链段运动的不同程度的固定。测量了一系列跨越零结晶度范围的标题共聚物的介电弛豫（具有2，5-己二醇的均聚物）至约60%（具有1，6-己二醇的均聚物）。的数据进行了分析，结晶度的动力学参数（活化能和弛豫宽度）和平衡参数（偶极子相关因子推导出的弛豫强度）的影响。在后一种情况下，应特别注意适当评估复合材料混合物对松弛强度的影响。β过程的形状对结晶度极其敏感，随着结晶度的出现而大大加宽，并且随着结晶度的增加而加宽。尽管β弛豫偶极相关因子不如宽度敏感，但它也取决于结晶度，结晶样品中无定形部分内链构型的可用性显著降低。γ过程动力学参数对晶相的存在相对不敏感，这一行为与局部运动机制一致。如果假设2，5二醇单元对松弛强度的贡献小于1，6二醇单元，则γ松弛强度与具有无定形相起源的过程相关;该结果也与局部运动概念一致。
Linear aliphatic polyesters are interesting model systems for studying relaxation processes in crystalline polymers because they show both γ and β relaxations in a prominent way whereas in many highly crystalline linear polymers (LPE, POM etc.) the β process is suppressed and, unlike branched polyethylene which also has a prominent β process, the polyesters have no chemical structural complications due to branches. To study the hypothesis that variations in the appearance of the β (glass-rubber) relaxation are due to varying degrees of immobilization of long-range segmental motion in the amorphous fraction by the presence of the crystal phase measurements are made of dielectric relaxation in a series of the title copolymers that span the crystallinity range of zero (homopolymer with 2,5-hexanediol) to ≈60% (homopolymer with 1,6-hexanediol). The data are analysed in terms of the effect of degree of crystallinity on both kinetic parameters (activation energies and relaxation width) and equilibrium parameters (dipole correlation factor deduced from relaxation strength). In the latter case special care is taken to properly assess composite mixture effects on the relaxation strength. The shape of the β process is extremely sensitive to the degree of crystallinity, broadening greatly with the onset of the presence of crystallinity and increasing in broadness with increasing degree of crystallinity. Although less sensitive than the width, the β relaxation dipole correlation factor depends on crystallinity also, the availability of chain configurations within the amorphous fraction being noticeably reduced in the crystalline specimens. The γ process kinetic parameters are relatively insensitive to the presence of the crystal phase, a behaviour consistent with a localized motion mechanism. The γ relaxation strength correlates with the process having an amorphous phase origin if it is assumed that the 2,5 diol units contribute less to relaxation strength than the 1,6 diol units; a result also consistent with the localized motion concept.