Strain-induced structural and dynamic changes in segmented polyurethane elastomers
Strain-induced structural and dynamic changes in segmented polyurethane elastomers
复制标题
分段聚氨酯弹性体中应变引起的结构和动态变化
DOI：
10.1016/j.polymer.2018.12.062
复制
发表时间：
2019-02
期刊：
影响因子：
4.6
通讯作者：
Pingchuan Sun
中科院分区：
文献类型：
--
作者：
Fenfen Wang;Shengli Chen;Qiang Wu;Rongchun Zhang;Pingchuan Sun
聚氨酯弹性体由于其多种多样的物理和化学性能，在工业和日常生活中得到了广泛的应用。因此，在分子水平上对结构和动力学的基本理解将为新型聚氨酯材料的精确设计和应用提供深刻的见解。在本研究中，我们主要研究了由聚ε-己内酯（PCL）和4,4 ' -二苯基亚甲基二异氰酸酯（MDI）分别作为软段和硬段组成的典型聚氨酯弹性体在应变诱导下的结构和动态变化。在力学拉伸试验中观察到明显的应变硬化现象，并对断裂试样和原始试样进行了系统的对比。DSC结果表明，试样断裂后PCL链仍在继续结晶，在25 ℃下物理时效2天后，晶体结构趋于稳定。1H固态核磁共振（NMR）实验进一步测定了拉伸过程中可移动PCL链转化为晶体的比例。此外，断裂样品的微相分离也明显增强。1h magic-sandwich echo (MSE) NMR实验表明，由于应变诱导的PCL片段结晶，非晶态PCL链的迁移率大大降低。1H多量子核磁共振（MQ）实验还定量揭示了断裂样品中无定形PCL链的应变诱导取向，表明当样品断裂时，PCL晶体起到了物理交联的作用，阻止了拉长的PCL链的收缩。
Polyurethane elastomers have been widely used in the industry and daily life due to their versatile physical and chemical properties. Therefore, a fundamental understanding of the structures and dynamics at a molecular level will provide piercing insights into the precise design and application of new polyurethane materials. In this study, we mainly focused on investigating the strain-induced structural and dynamic changes in a typical polyurethane elastomer composed of poly(ε-caprolactone) (PCL) and 4,4′-diphenylmethylene diisocyanate (MDI) as the soft and hard segments, respectively. Obvious strain-hardening phenomenon was observed during the mechanical tensile test, and a systematic comparison was performed on the fractured and pristine samples. DSC results revealed that the crystallization of PCL chains was still going on after the sample was fractured, and the crystallite structures became stable after physical aging at 25 °C for two days.1H solid-state nuclear magnetic resonance (NMR) experiment was further employed to determine the fraction of mobile PCL chains that were converted to crystallites during stretching. Besides, the microphase separation was also significantly enhanced in the fractured sample. The mobility of amorphous PCL chains was largely reduced due to the strain-induced crystallization of nearby PCL segments, as revealed by the1H magic-sandwich echo (MSE) NMR experiments.1H multiple quantum (MQ) NMR experiments also quantitatively revealed the strain-induced orientation of amorphous PCL chains in the fractured sample, indicating that the PCL crystallites were acting as the physical cross-linkages to prevent the contraction of the elongated PCL chains when the sample is fractured.
登录
查看更多内容
影响因子：
6
作者：
D. Randall;Steve Lee
通讯作者：
D. Randall;Steve Lee
基于可逆 CC 键的机械坚固、可自修复且高度可拉伸的“活性”交联聚氨酯
影响因子：
19
作者：
Zhang Ze Ping;Rong Min Zhi;Zhang Ming Qiu
通讯作者：
Zhang Ming Qiu
影响因子：
5.5
作者：
Waletzko, Ryan S.;Korley, LaShanda T. James;hammond, Paula T.
通讯作者：
hammond, Paula T.
影响因子：
29.4
作者：
Shen Yu;Rongchun Zhang;Qiang Wu;Tiehong Chen;Pingchuan Sun
通讯作者：
Shen Yu;Rongchun Zhang;Qiang Wu;Tiehong Chen;Pingchuan Sun
基于热可逆Diels-Alder反应和分子链热运动双重作用的聚氨酯自修复行为
影响因子：
4.6
作者：
Feng, Libang;Yu, Zhengyang;Chai, Changsheng
通讯作者：
Chai, Changsheng