具有阴离子聚合的丁苯橡胶的量身定制的动态液晶网络，可调节形状记忆和自我修复能力,Macromolecules

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具有阴离子聚合的丁苯橡胶的量身定制的动态液晶网络，可调节形状记忆和自我修复能力
Macromolecules ( IF 5.1 ) Pub Date : 2021-03-04 , DOI: 10.1021/acs.macromol.0c02741
Lan Lei ₁ , Li Han ₁ , Hongwei Ma ₁ , Ruixue Zhang ₁ , Xuwen Li ₁ , Songbo Zhang ₁ , Chao Li ₁ , Hongyuan Bai ₁ , Yang Li ₁

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具有同时分子迁移和机械增强的液晶网络（LCN）的量身定制的结构是理想的。由于聚合物材料的性能很大程度上取决于聚合物链的分子组成，因此在本工作中，我们证明了控制良好的75 wt％丁二烯对阴离子聚合的无规丁苯橡胶（r -SBR）的调谐组成合成（Bd）提供分子迁移性的内含物。51.5–64.0 mol％的微结构1,2-烯烃被设计为连接50 mol％SiH封端的介晶基团（M）沿着Bd单元使用氢化硅烷化。由于机械强度通常与高分子迁移率相冲突，因此，从动态2（6-异氰酸根己基氨基羰基氨基）-6-甲基-4 [ 1H ]-嘧啶酮（UPy-NCO）的不同比例中有序LC堆叠和同时交联得到的集成设计Bd单元的1,4-烯烃上的永久六亚甲基二异氰酸酯（HMDI）提供必要的机械强度和分子迁移率，从而产生一系列动态LCN（r -SBR- g- [M·HMDI·UPy]）。LC纹理，相变，自愈/焊接和形状记忆能力得到了全面的研究。所有LCN都在T _i附近的POM中显示LC纹理（42–53°C），由于50 mol％的有序LC堆积，绝对有助于机械性能和分子迁移率。形成动态H键的Ureidopyrimidinoneone（UPy）有利于暂时的形状固定率（R _f），可回收性和自愈/焊接能力，同时降低了形状恢复率（R _rec），因为UPy可以增加断裂伸长率，但牺牲机械强度。但是，形成共价交联键的HMDI却显示相反的效果，因为HMDI可以有效增强机械强度，但会降低链迁移率。有证据表明，r -SBR 45k - g- [M-0％，2％]几乎不发生形状恢复（R_rec = 0），尽管R _f = 92.6％，而对于r -SBR 45k - g- [M-10％，2％]，R _rec大大提高到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/焊接效率。这表明分子组成对性能的协同作用。通过定量合成对聚合物链结构进行量身定制的结构被证明是控制性能的有效策略。

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Well-Tailored Dynamic Liquid Crystal Networks with Anionically Polymerized Styrene-Butadiene Rubbers toward Modulating Shape Memory and Self-Healing Capacity

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)-6-methyl-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 °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.

更新日期：2021-03-23

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