Measuring Tie Chains and Trapped Entanglements in Semicrystalline Polymers†,Macromolecules

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Measuring Tie Chains and Trapped Entanglements in Semicrystalline Polymers†
Macromolecules ( IF 5.1 ) Pub Date : 2020-06-19 , DOI: 10.1021/acs.macromol.0c00132
Amanda G. McDermott ₁ , Paul J. DesLauriers ₂ , Jeff S. Fodor ₂ , Ronald L. Jones ₁ , Chad R. Snyder ₁

Affiliation

A label-free method for quantifying stress transmitter (or elastically effective molecule) content (p) in semicrystalline polymers, including both tie molecules and bridging entanglements, is developed and demonstrated based on swelling with deuterated vapor and characterization with small-angle neutron scattering. The p results are compared with the predictions of recent semiempirical, statistical values for tie molecule content and structural characterization parameters, including strain hardening modulus and an infrared-spectroscopy-derived parameter (β) that describes the degree of difficulty for the amorphous content to align and reshape over a distance with the applied load. A strong correspondence is observed, suggesting that the initial network of elastically active molecules, dictated by the molecular architecture and crystallization conditions, can be directly correlated to the postyield tensile values irrespective of the subsequent morphological changes that result during the tensile deformation. These comparisons are also consistent with simulations, indicating that polyethylene homopolymers have more bridging entanglements than copolymers and that the average tie molecule has a larger impact on the mechanical properties than the average bridging entanglement. Contrary to high-temperature bulk swelling measurements, it is found that the Michaels–Hausslein vapor swelling theory cannot fit the experimental data, while our modified Flory–Rehner theory can fit the data.

中文翻译：

测量半结晶聚合物中的拉链和捕获缠结†

基于氘化蒸气的溶胀和小角中子散射的表征，开发并演示了一种用于量化半结晶聚合物（包括连接分子和桥接纠缠）中应力递质（或弹性有效分子）含量（p）的无标记方法。将 p 结果与最近对 tie 分子含量和结构表征参数的半经验统计值的预测进行了比较，包括应变硬化模量和红外光谱衍生参数（β），该参数描述了无定形内容物在一定距离内与施加的载荷对齐和重塑的难度。观察到很强的对应关系，表明由分子结构和结晶条件决定的弹性活性分子的初始网络可以直接与屈服后的拉伸值相关，而不管拉伸变形过程中导致的后续形态变化如何。这些比较也与模拟一致，表明聚乙烯均聚物比共聚物具有更多的桥接缠结，并且平均连接分子对机械性能的影响比平均桥接缠结更大。与高温体溶胀测量相反，发现 Michaels-Hausslein 蒸汽溶胀理论不能拟合实验数据，而我们改进的 Flory-Rehner 理论可以拟合数据。

更新日期：2020-07-14

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