Evaluations of Mesogen Orientation near the Substrate Surface in Thin Films of Polyacrylate with Cyanobiphenyl Side Chain
Evaluations of Mesogen Orientation near the Substrate Surface in Thin Films of Polyacrylate with Cyanobiphenyl Side Chain
复制标题
氰基联苯侧链聚丙烯酸酯薄膜基体表面附近介晶取向的评价
DOI：
10.1021/acs.langmuir.6b00538
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发表时间：
2016
期刊：
影响因子：
3.9
通讯作者：
Takahiro Seki
中科院分区：
文献类型：
--
作者：
Daisuke Tanaka;Takumi Mizuno;Mitsuo Hara;Shusaku Nagano;Itsuki Saito;Katsuhiro Yamamoto;Takahiro Seki
采用紫外-可见吸收光谱和掠入射小角X射线散射（GI-SAXS）方法，分别用高能Cu Kα线（λ = 0.154 nm）和低能同步辐射X射线（λ = 0.539 nm）研究了含氰基联苯（CB）侧链的聚丙烯酸酯薄膜中液晶基元的取向行为。通过改变薄膜厚度在7-200 nm范围内，可以得出结论，对于厚度小于10-15 nm的薄膜，平面取向占主导地位。在厚度大于30 nm的薄膜中，这种靠近衬底表面的平面介晶取向与垂直取向的CB介晶共存。对于最薄的7 nm膜，意外地失去了平面取向，这与近晶层结构的无序相伴随。CB介晶的特殊取向特性的建议，这可能是源于由于末端氰基的强偶极矩形成一个反平行排列的介晶的倾向。
The orientation behavior of mesogens in a polyacrylate with cyanobiphenyl (CB) side chain in thin films was investigated in detail by UV–vis absorption spectroscopy and grazing incidence small-angle X-ray scattering (GI-SAXS) measurements using both high-energy X-rays of Cu Kα line (λ = 0.154 nm) and low-energy synchrotron X-rays (λ = 0.539 nm). By changing the film thickness ranging 7–200 nm, it is concluded that the planar orientation is predominant for thin films with thickness below 10–15 nm. This planar mesogen orientation near the substrate surface coexists with the homeotropically aligned CB mesogens in films thicker than 30 nm. For the thinnest 7 nm film, the planar orientation is unexpectedly lost, which is in consort with a disordering of smectic layer structure. Peculiar orienting characteristics of CB mesogen are suggested, which probably stem from the tendency to form an antiparallel arrangement of mesogens due to the strong dipole moment of the terminal cyano group.