Angel Alegría*, Arantxa Arbe, Juan Colmenero, Saibal Bhaumik, Konstantinos Ntetsikas and Nikos Hadjichristidis*,
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引用次数: 0
摘要
聚合物玻璃体是一类兼具热塑性塑料和热固性塑料优点的新型材料。这是由于连接不同链的化学键具有动态性质。然而,这一特性如何影响聚合物在不同长度尺度上的动力学仍是一个未决问题。在此,我们使用宽带介电光谱法研究了基于定义明确的聚异戊二烯(PI)链的模型玻璃体的动力学。通过这种方法,我们利用聚异丁烯属于一类表现出与端到端矢量相关的净偶极矩的分子这一事实,研究了从分段到整链尺度的聚合物动力学。研究发现了三种不同的松弛现象。最快的弛豫归因于分段 PI 动力学,交联的影响较小。此外,还观察到交联剂偶极特性引起的中间弛豫。与端到端 PI 链的有限波动相对应的较慢弛豫成分是由交联剂形成的簇的动力学决定的,其平均时间尺度比从粘性流动推断的末端弛豫快几个数量级。
Segmental and Chain Dynamics of Polyisoprene-Based Model Vitrimers
Polymer vitrimers are a new class of materials that combine the advantages of thermoplastics and thermosets. This is due to the dynamic nature of the chemical bonds linking different chains. However, how this property affects the polymer dynamics at different length scales is still an open question. Here, we investigate the dynamics of model vitrimers based on well-defined polyisoprene (PI) chains using broadband dielectric spectroscopy. In this way, we study the polymer dynamics from the segmental to the whole chain scale, taking advantage of the fact that PI belongs to the class of molecules that exhibit a net dipole moment associated with the end-to-end vector. Three distinct relaxation phenomena are identified. The fastest relaxation is attributed to the segmental PI dynamics with a small influence of the cross-linking. An intermediate relaxation attributed to the dipolar character of the cross-linker is also observed. The slower identified relaxation component, corresponding to limited fluctuations of the end-to-end PI chains, is found to be determined by the dynamics of the clusters formed by the cross-linkers with an average time scale orders of magnitude faster than that of the terminal relaxation as inferred from the viscous flow.
期刊介绍:
Macromolecules publishes original, fundamental, and impactful research on all aspects of polymer science. Topics of interest include synthesis (e.g., controlled polymerizations, polymerization catalysis, post polymerization modification, new monomer structures and polymer architectures, and polymerization mechanisms/kinetics analysis); phase behavior, thermodynamics, dynamic, and ordering/disordering phenomena (e.g., self-assembly, gelation, crystallization, solution/melt/solid-state characteristics); structure and properties (e.g., mechanical and rheological properties, surface/interfacial characteristics, electronic and transport properties); new state of the art characterization (e.g., spectroscopy, scattering, microscopy, rheology), simulation (e.g., Monte Carlo, molecular dynamics, multi-scale/coarse-grained modeling), and theoretical methods. Renewable/sustainable polymers, polymer networks, responsive polymers, electro-, magneto- and opto-active macromolecules, inorganic polymers, charge-transporting polymers (ion-containing, semiconducting, and conducting), nanostructured polymers, and polymer composites are also of interest. Typical papers published in Macromolecules showcase important and innovative concepts, experimental methods/observations, and theoretical/computational approaches that demonstrate a fundamental advance in the understanding of polymers.