Small-molecule dynamics and mechanisms underlying the macroscopic mechanical properties of coordinatively cross-linked polymer networks
Small-molecule dynamics and mechanisms underlying the macroscopic mechanical properties of coordinatively cross-linked polymer networks
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DOI：
10.1021/ja054298a
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发表时间：
2005-10-19
影响因子：
15
通讯作者：
Craig, SL
中科院分区：
文献类型：
--
作者：
Yount, WC;Loveless, DM;Craig, SL
双钯（II）和铂（II）有机金属交联剂与DMSO中的聚（4-乙烯基吡啶）之间的特定金属配位定义了三维结合聚合物网络。通过测量模型Pd（II）和Pt（II）配合物上的吡啶交换率，发现一系列四种不同体材料的频率相关动态力学模量在几十年的振荡应变速率下测量。重要的是，网络中的配体交换机制与模型配合物中观察到的溶剂辅助途径相同，因此，当交联从聚合物主链解离时发生的弛豫决定了整体机械性能。是交联键解离的频率，而不是它们保持解离的时间，决定了材料的整体力学性能。在模型化合物中观察到的大块材料性能与动力学和机制之间的定量关系为具有定制力学性能的材料的合理分子设计带来了希望。
Specific metal-ligand coordination between bis-Pd(II) and Pt(II) organometallic cross-linkers and poly(4-vinylpyridine) in DMSO defines a three-dimensional associative polymer network. Frequency-dependent dynamic mechanical moduli of a series of four different bulk materials, measured across several decades of oscillatory strain rates, are found to be quantitatively related through the pyridine exchange rates measured on model Pd(II) and Pt(II) complexes. Importantly, the mechanism of ligand exchange in the networks is found to be the same solvent-assisted pathway observed in the model complexes, and so the bulk mechanical properties are determined by relaxations that occur when the cross-links are dissociated from the polymer backbone. It is how often the cross-links dissociate, independently of how long they remain dissociated, that determines the bulk mechanical properties. The quantitative relationship between bulk materials properties and the kinetics and mechanisms observed in model compounds holds promise for the rational, molecular design of materials with tailored mechanical properties.