Vitrimers of polyolefin elastomer with physically cross-linked network
Vitrimers of polyolefin elastomer with physically cross-linked network
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DOI：
10.1007/s10965-021-02573-3
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发表时间：
2021-05
影响因子：
2.8
通讯作者：
Wei-Yu Wang;Xiangjun Zha;Rui‐Ying Bao;Kai Ke;Zhengying Liu;Ming‐bo Yang;Wei Yang
中科院分区：
文献类型：
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作者：
Wei-Yu Wang;Xiangjun Zha;Rui‐Ying Bao;Kai Ke;Zhengying Liu;Ming‐bo Yang;Wei Yang
当硼酸酯键作为物理交联键引入到具有结晶相的热塑性弹性体中时，参与交换反应的化学物种的流动性影响了玻璃化物网络内的交换动力学，然后它可以受到结晶相的影响。本文将二氧硼杂环戊烷动态交联引入到商品化聚乙烯-α-辛烯（POE）中，以结晶相作为物理交联剂，制备POE玻璃化聚合物。应力松弛的结果表明，在熔融温度范围内，无论是动态交联的POE玻璃化物和热处理的POE玻璃化物，还是纯物理交联的纯POE，其应力松弛时间（τ）与温度均符合Arrhenius定律。由于残余结晶相的限制流动性，POE玻璃化物的液-固转变温度可以从热处理的-42.9 °C升高到35.3 °C。所得POE玻璃化物在室温下保持高于27.5MPa的断裂应力和高于800%的断裂伸长率。随着温度的升高，POE中物理交联的减弱导致强度降低，但储能模量和300%和500%伸长率下的应力提高。POE玻璃化聚合物在回收或修复后性能几乎保持不变。这些结果表明，可逆硼酸酯键的引入是一种很有前途的策略，以提高物理交联POE材料的性能和可回收性。
Dynamics of exchange within vitrimer networks are influenced by mobility of the chemical species involved in the exchange reaction, then it can be affected by the crystalline phase when boronic ester bond is introduced into the thermoplastic elastomers with crystalline phase as physical cross-links. In this work, the dynamic dioxaborolane cross-links were introduced into commercial poly(ethylene-α-octene) (POE) with crystalline phases as physical cross-links to prepare POE vitrimers. The results of stress relaxation show that relaxation time (τ) follows an Arrhenius law with the temperature at the melting range for not only POE vitrimers and thermally treated POE vitrimers with dynamic cross-links, but also neat POE with purely physical cross-links. The liquid-to-solid transition temperature can raise to 35.3 °C for POE vitrimers from -42.9 °C of the thermally treated one, due to the constrained mobility by residual crystalline phases. The resulted POE vitrimers maintain a stress at break of higher than 27.5 MPa and an elongation at break of higher than 800% at room temperature. With the temperature increasing, the crystal melting induced weakening of the physical cross-linking in POE decreases the strength, but the storage modulus and the stress at 300% and 500% elongation of POE vitrimers are improved. The properties of POE vitrimers can almost keep unchanged after recycling or healing. All these results show that the introduction of reversible boronic ester bonds is a promising strategy to improve the performances and recyclability of physically cross-linked POE materials.