Normally Oriented Cylindrical Nanostructures in Amphiphilic PEO-LC Diblock Copolymers Films
Normally Oriented Cylindrical Nanostructures in Amphiphilic PEO-LC Diblock Copolymers Films
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DOI：
10.1021/ma201119u
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发表时间：
2011-10-11
期刊：
影响因子：
5.5
通讯作者：
Yoshida, Hirohisa
中科院分区：
文献类型：
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作者：
Asaoka, Sadayuki;Uekusa, Takayuki;Yoshida, Hirohisa
两亲性二嵌段共聚物由聚（环氧乙烷）（PEO）和聚（甲基丙烯酸酯）（PMA）组成，在侧链中具有偶氮苯作为介晶单元，提供高度有序的相分离纳米结构，其中PEO圆柱域呈六角形排列，并且通常在薄膜中的PMA基质中取向。强偏析嵌段共聚物中的液晶有序性对于获得如此优异的纳米结构排列起着最重要的作用，这可能导致实际应用。为了阐明PMA链段侧链中介晶单元的作用，合成了一系列新的两亲性液晶二嵌段共聚物，以偶氮苯、亚苄基苯胺和二苯乙烯作为介晶核来调节液晶链段中介晶单元之间的分子相互作用。所有侧链液晶二嵌段共聚物均表现出近晶相，并在块状颗粒中呈现六边形排列的圆柱形纳米结构。具有4-(4-丁基苯基偶氮)苯氧基、4-((E)-(4-丁基苯基亚氨基)甲基)苯氧基或44(E)-4-丁基苯乙烯基)苯氧基作为介晶单元的嵌段共聚物在薄膜中给出了高度有序的六方纳米圆柱结构，而具有(E)-4-(4-丁基苯亚甲基氨基)苯氧基介晶基团的共聚物提供了不太有序的纳米结构。前三种共聚物在退火薄膜的紫外-可见光谱上表现出明显的减色位移和较大的减色效应，这意味着PMA基体中介晶部分形成了强H聚集和垂直排列。
The amphiphilic diblock copolymers consist of poly(ethylene oxide) (PEO) and poly(methacrylate) (PMA) having azobenzenes as mesogen units in the side chain afford highly ordered phase-segregated nanostructures, in which PEO cylindrical domains are hexagonally arranged and normally oriented in PMA matrix in the thin films. The liquid crystalline ordering in the strongly segregated block copolymers plays one of the most important roles to attain such an excellent arrangement of the nanostructure potentially leading to practical use. In order to elucidate the role of the mesogen units in the side chain of the PMA segment, a new series of amphiphilic liquid crystalline diblock copolymers were synthesized to tune molecular interaction between mesogen units in liquid crystalline segments by using azobenzene, benzylideneaniline, and stilbene as mesogen cores. All the side-chain liquid crystalline diblock copolymers exhibited smectic phase and gave hexagonally arranged cylindrical nanostructures in the bulk pellets. The block copolymers having 4-(4-butylphenylazo)phenoxy, 4-((E)-(4-butylphenylimino)methyl)Phenoxy, or 44(E)-4-butylstyryl)phenoxy groups as the mesogens units gave the highly ordered hexagonal nanocylinder structures in thin film, while the copolymers having (E)-4-(4-butylbenzylideneamino)phenoxy mesogen group afforded less ordered nanostructures. The former three kinds of copolymers showed obvious hypsochromic shifts and large hypochromic effects on the UV-vis spectra of annealed film, implying the formation of the strongly H-aggregated and homeotropic alignment of mesogen moieties in the PMA matrix.