Well-Tailored Dynamic Liquid Crystal Networks with Anionically Polymerized Styrene-Butadiene Rubbers toward Modulating Shape Memory and Self-Healing Capacity
Well-Tailored Dynamic Liquid Crystal Networks with Anionically Polymerized Styrene-Butadiene Rubbers toward Modulating Shape Memory and Self-Healing Capacity
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采用阴离子聚合丁苯橡胶精心定制的动态液晶网络，可调节形状记忆和自愈能力
DOI：
10.1021/acs.macromol.0c02741
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发表时间：
2021-03-04
期刊：
影响因子：
5.5
通讯作者：
Li, Yang
中科院分区：
文献类型：
--
作者：
Lei, Lan;Han, Li;Li, Yang
同时具有分子移动性和机械增强的液晶网络（LCN）的良好定制的构造是期望的。由于聚合物材料的性能在很大程度上取决于聚合物链的分子组成，因此在本工作中，我们展示了阴离子聚合无规苯乙烯-丁二烯橡胶（r-SBRs）的调整组成合成，其中丁二烯（Bd）含量控制良好，为75wt%，提供分子流动性。设计51.5-64.0摩尔%的微结构1，2-烯烃以使用氢化硅烷化将50摩尔% SiH封端的介晶部分（M）沿着Bd单元连接。由于机械强度通常与高分子流动性相冲突，因此通过有序的LC堆叠和同时交联以不同的动态2（6-异氰酸根合己基氨基羰基氨基）-6甲基-4[1H]-嘧啶酮（UPy-NCO）和永久二异氰酸酯（HMDI）与Bd单元的1，4-烯烃一起沿着提供必要的机械强度和分子流动性，产生一系列动态LCN（r-SBR-g-[M.HMDI.UPy]）。LC织构，相变，自愈合/焊接，和形状记忆能力进行了全面的研究。所有LCN在T1（42- 53 ° C）附近在POM中显示出LC织构，由于50摩尔%有序的LC堆叠，这肯定有助于机械性能和分子移动性。形成动态H键的脲基嘧啶酮（UPy）有益于暂时形状固定率（R-f）、可再循环性和自愈合/焊接能力，同时降低形状恢复率（R-rec），因为UPy可以增加断裂伸长率但牺牲机械强度。然而，形成共价交联的HMDI表现出相反的效果，因为HMDI可以有效地提高机械强度，但降低链的流动性。结果表明，尽管R-f = 92.6%，r-SBR 45 k-g-[M-0%，2%]几乎不经历形状回复（R-rec = 0），而对于r-SBR 45 k-g-[M-10%，2%]，R-rec大大增加到100%，但R-f降低到46.2%。除r-SBR-g-[M-10%，2%]外，所有LCN均显示出高于82%的自愈合/焊接效率。这表明了分子组成对性能的协同作用。通过定量合成的聚合物链结构的量身定制的建设被证明是一个强大的战略操纵性能。
Well-tailored construction of liquid crystal networks (LCNs) with simultaneous molecular mobility and mechanical enhancement is desirable. Since the properties of polymeric materials are largely a result of the molecular compositions of polymer chains, in the present work, we demonstrate the tuning compositional synthesis of anionically polymerized random styrene-butadiene rubbers (r-SBRs) with well-controlled 75 wt % butadiene (Bd) contents that offer molecular mobility. Microstructural 1,2-olefins of 51.5-64.0 mol % were designed to attach 50 mol % SiH-terminated mesogenic moieties (M) along Bd units using hydrosilylation. As mechanical strength usually conflicts with high molecular mobility, an integrated design derived from the orderly LC stacking and simultaneous crosslinking in various ratios of the dynamic 2(6-isocyanatohexylaminocarbonylamino)-6methyl-4[1H]-pyrimidinone (UPy-NCO) and permanent hexamethylene diisocyanate (HMDI) along 1,4-olefins of Bd units offers necessary mechanical strength and molecular mobility, resulting in a series of dynamic LCNs (r-SBR-g-[M.HMDI.UPy]). LC textures, phase transitions, self-healing/welding, and shape memory capacities were comprehensively studied. All LCNs showed LC textures in POM around T-i (42- 53 degrees C), which definitely contributed to both mechanical performance and molecular mobility due to the 50 mol % orderly LC stacking. Ureidopyrimidinone (UPy) that forms a dynamic H-bond is beneficial for the temporary shape fixity ratio (R-f), recyclability, and self-healing/welding ability while decreasing the shape recovery ratio (R-rec) because UPy can increase breaking elongations but sacrifice the mechanical strength. However, HMDI that forms a covalent crosslink showed the contrary effect, as HMDI can effectively enhance the mechanical strength but reduce the chain mobility. It is evidenced that r-SBR45k-g-[M-0%, 2%] can hardly undergo shape recovery (R-rec = 0) despite R-f = 92.6%, while with regard to r-SBR45k-g-[M-10%, 2%], R-rec greatly increased to 100%, but R-f decreased to 46.2%. All LCNs showed a higher than 82% self-healing/welding efficiency, with an exception of r-SBR-g-[M-10%, 2%]. This indicated the cooperative effect of molecular compositions on the properties. The well-tailored construction of polymer chain architecture through quantitative synthesis proves to be a powerful strategy for manipulating properties.