Synthesis and phase structures of combined main-chain/side-chain liquid crystalline polymers with different-number azobenzene moiety in the side-chain based on mesogen-jacketed liquid crystalline polymers
Synthesis and phase structures of combined main-chain/side-chain liquid crystalline polymers with different-number azobenzene moiety in the side-chain based on mesogen-jacketed liquid crystalline polymers
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DOI：
10.1080/02678292.2013.824121
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发表时间：
2013-11
期刊：
影响因子：
2.2
通讯作者：
Chang-an Yang;He-Lou Xie;Sheng Chen;Hailiang Zhang
中科院分区：
文献类型：
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作者：
Chang-an Yang;He-Lou Xie;Sheng Chen;Hailiang Zhang
合成了三种不同重复单元侧链含不同数目偶氮苯液晶基元的主链/侧链复合型液晶聚合物。这些是聚（2，5-双{[3-（4′-甲氧基-4-氧己氧基偶氮苯）苄基]氧羰基}苯乙烯）（表示为PABCS）、聚（2，5-双{[3，5-二（4′-甲氧基-4-氧己氧基偶氮苯）苄基]氧羰基}苯乙烯）（表示为PDABCS）和聚（2，5-双{[3，4，5-三（4′-甲氧基-4-氧己氧基偶氮苯）苄基]氧羰基}苯乙烯）（表示为PTABCS）。单体的化学结构经1H NMR和13 C NMR确证。通过1H NMR和凝胶渗透色谱（GPC）对聚合物的结构进行了表征，并利用差示扫描量热法（DSC）、偏光显微镜（PLM）和一维广角X射线衍射（WAXD）对聚合物的相结构和相转变进行了研究。结果表明，在主链/侧链复合液晶聚合物中，每个重复单元中侧链上偶氮苯液晶基元的数目对液晶相类型的选择起着重要的控制作用，随着偶氮苯液晶基元数目的增加，聚合物显示出更加多样和有趣的液晶性质.首先，PABCS的主链构建了一个二维中心矩形（ΦR）支架，并且在各向同性温度（Ti）以下，含偶氮苯的侧链在主链支架内的堆积形成了smecitc A（SmA）样结构。其次，随着偶氮苯介晶数目的增加，PDABCS的主链在低温下形成二维中心矩形（ΦR）骨架，在高温下形成二维六方柱状（ΦH）相，主链骨架中侧链的堆积经历了SmA类参与各向同性的转变。第三，对于PTABCS，相变顺序如下：2D中心矩形柱相（ΦR）主链骨架和侧链SmB样结构Particip 2D中心矩形柱相（ΦR）主链骨架和侧链SmA样结构Particip 2D中心矩形柱相（Φ R）主链骨架和各向同性侧链Particip 2D长程有序六方柱相（ΦH）主链和各向同性的侧链。聚合物PDABCS和PTABCS的二维长程有序ΦH相在样品完全分解之前仍然存在。
Three novel combined main-chain/side-chain liquid crystalline polymers with different number of azobenzene mesogens in the side chain per repeating unit have been synthesised. These are poly(2,5-bis{[3-(4′-methoxy-4-oxyhexyloxy azobenzene)benzyl]oxycarbonyl}styrene) (denoted as PABCS), poly(2,5-bis{[3,5-di(4′-methoxy-4-oxyhexyloxy azobenzene)benzyl]oxycarbonyl}styrene) (denoted as PDABCS) and poly (2,5-bis{[3,4,5-tri(4′-methoxy-4-oxyhexyloxy azobenzene)benzyl]oxycarbonyl}styrene) (denoted as PTABCS). The chemical structure of the monomers was confirmed by 1H NMR and 13C NMR. The structural characterisation of the polymers was performed by 1H NMR and gel permeation chromatography (GPC), and the phase structures and transitions of the polymers were studied using differential scanning calorimetry (DSC), polarised light microscopy (PLM) and one-dimensional (1D) wide-angle X-ray diffraction (WAXD). The results show that the number of azobenzene mesogens in the side chain per repeating unit in the combined main-chain/side-chain liquid crystalline polymers plays an important role in dominating the phase type preferences, and the polymers exhibit more versatile and intriguing liquid crystalline properties with increasing number of azobenzene mesogens. First, the main chains of PABCS construct a 2D-centred rectangular (ΦR) scaffold and the packing of azobenzene-containing side chains inside the main-chain scaffold develops smecitc A (SmA)-like structure below isotropic temperature (Ti). Second, with increasing the number of azobenzene mesogens, the main chains of PDABCS develop a 2D-centred rectangular (ΦR) scaffold at lower temperature and a 2D hexagonal columnar (ΦH) phase at higher temperature, and the packing of side chains inside the main-chain scaffold undergoes the transition of SmA-like ↔ isotropic. Third, for PTABCS, the sequence of phase transitions followed is: 2D centred rectangular columnar phase (ΦR) scaffold of main chain and SmB-like structure of side chain ↔ 2D centred rectangular columnar phase (ΦR) scaffold of main chain and SmA-like structure of side chain ↔ 2D centred rectangular (ΦR) scaffold of main chain and isotropic side chain ↔ 2D long-range-ordered hexagonal columnar phase (ΦH) of main chain and isotropic side chain. The 2D long-range-ordered ΦH phases of the polymers PDABCS and PTABCS still remain before the samples are completely decomposed.