Precise polyethylene derivatives bearing mesogenic side-chains: delicate self-assembly depending on graft density
Precise polyethylene derivatives bearing mesogenic side-chains: delicate self-assembly depending on graft density
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DOI：
10.1039/c9py01856e
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发表时间：
2020-02
影响因子：
4.6
通讯作者：
Wenying Chang;Dong Shi;Xuqiang Jiang;Jiadi Jiang;Yang Zhao;Xiang-Kui Ren;Shuang Yang;E. Chen
中科院分区：
文献类型：
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作者：
Wenying Chang;Dong Shi;Xuqiang Jiang;Jiadi Jiang;Yang Zhao;Xiang-Kui Ren;Shuang Yang;E. Chen
为了实现侧链聚合物的理想性能，精心控制聚合物主链和侧链之间的相互作用至关重要，这可以通过调整侧链的接枝密度来实现。在此，我们报道了一系列芳香族联苯侧链沿脂肪族主链精确接枝在每第2个、第7个和第15个碳（Pns，n = 2、7和15）上的聚乙烯衍生物，其接枝密度分别接近每纳米4、1和0.5个侧链。使用各种技术研究了 Pns 的自组装结构和相变。我们证明，精确调整两个相邻侧链之间的距离，即侧链间距，可以极大地改变主链和棒状介晶侧链的局部耦合，导致不同的主链构象和各向异性相互作用。与形成晶体E相的普通侧链液晶聚合物（SCLCP）P2相比，P7和P15分别表现出三维（3D）有序结构KX和二维（2D）矩形柱状相ColR，这在SCLCP中是前所未有的。此外，当接枝密度变化时，相变途径也可以显着改变。
To achieve desirable properties of side-chain polymers, elaborately manipulating the interplay between the polymer backbone and side-chains is vital, which can be done by adjusting the graft density of side-chains. Here, we report a series of polyethylene derivatives with the aromatic biphenyl side-chains precisely grafted on every 2nd, 7th and 15th carbon (Pns, n = 2, 7, and 15) along the aliphatic backbone, the graft densities of which are nearly 4, 1, and 0.5 side-chains per nanometer, respectively. The self-assembly structures and phase transitions of Pns were investigated using various techniques. We demonstrate that precisely adjusting the distance between two adjacent side-chains, i.e., the side-chain spacing, can drastically alter the local coupling of the backbone and rod-like mesogenic side-chains, leading to different backbone conformations and anisotropic interactions. Compared to P2 that is an ordinary side-chain liquid crystalline polymer (SCLCP) forming a crystal E phase, P7 and P15 exhibit a three-dimensionally (3D) ordered structure KX and a two-dimensional (2D) rectangular columnar phase ColR, respectively, which are unprecedented in SCLCPs. Moreover, the phase transition pathway can also be modified remarkably when the graft density is varied.