Effects of Oscillatory Shear on the Orientation of the Inverse Bicontinuous Cubic Phase in a Nonionic Surfactant/Water System
Effects of Oscillatory Shear on the Orientation of the Inverse Bicontinuous Cubic Phase in a Nonionic Surfactant/Water System
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振荡剪切对非离子表面活性剂/水体系中反双连续立方相取向的影响
DOI：
10.1021/acs.langmuir.5b04372
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发表时间：
2016
期刊：
影响因子：
3.9
通讯作者：
and T. Kato
中科院分区：
文献类型：
--
作者：
M. Yamanoi;Y. Kawabata;and T. Kato
两亲体系中形成的双连续反立方相（V2相）由长程有序的双层网络组成。采用流变学/小角X射线散射同时测量的方法，研究了振荡剪切对非离子表面活性剂（C12 E2）/水体系中空间群为Ia 3d的V2相取向的影响。结果表明，当应变幅（γ0）为20 μ m时，当损耗模量（G″）与储能模量（G′）之比（G″/G′ = tan δ）为100 μ m时，大振幅振荡剪切（LAOS）可以细化晶粒。另一方面，当在线性区域中的小振幅（γ0 ≤ 0.0004）振荡剪切（SAOS）施加于LAOS之后的样品时，立方晶格的取向发生。有趣的是，在SAOS之后，“中等振幅”（γ0 ≤ 0.05）振荡剪切（“MAOS”）强烈增强了取向。当在施加LAOS之前施加MAOS时，没有观察到向特定方向的取向，表明通过LAOS的晶粒细化过程对于MAOS期间的取向是必要的。实验结果表明，“LAOS-MAOS”剪切序列对立方晶格的取向是有效的。当LAOS和MAOS交替施加到样品时，晶粒细化和取向分别发生在LAOS和MAOS期间，表明取向的可逆性。结果表明：（i）取向度与γ 0和MAOS频率（ω）有关;（ii）γ 0和ω的组合可获得较高的取向度，tan δ = 2-3。晶格常数在整个剪切过程中没有变化，在实验误差范围内与剪切前的晶格常数相等，表明剪切熔融没有发生。这些结果表明，只有通过改变振荡剪切的条件，而不使用从其他各向异性相，如六方相和层状相的外延过渡控制的立方晶格的取向的可能性。
The bicontinuous inverse cubic phase (V2phase) formed in amphiphilic systems consists of bilayer networks with a long-range order. We have investigated effects of oscillatory shear on the orientation of the V2phase with space groupIa3dformed in a nonionic surfactant (C12E2)/water system by using simultaneous measurements of rheology/small-angle X-ray scattering. It is shown that grain refining occurs by applying the large amplitude oscillatory shear (LAOS) with a strain amplitude (γ0) of ∼20, which gives the ratio of the loss modulus (G″) to the storage modulus (G′) (G″/G′ = tan δ) of ∼100. On the other hand, orientation of the cubic lattice occurs when the small amplitude (γ0≈ 0.0004) oscillatory shear (SAOS) in the linear regime is applied to the sample just after the LAOS. Interestingly, the orientation is strongly enhanced by the “medium amplitude” (γ0≈ 0.05) oscillatory shear (“MAOS”) after the SAOS. When the MAOS is applied before applying the LAOS, orientation to a particular direction is not observed, indicating that the grain refining process by the LAOS is necessary for the orientation during the MAOS. The results of additional experiments show that the shear sequence “LAOS–MAOS” is effective for the orientation of the cubic lattice. When the LAOS and MAOS are applied to the sample alternatively, grain refining and orientation occur during the LAOS and MAOS, respectively, indicating reversibility of the orientation. It is shown that (i) the degree of the orientation is dependent on γ0and the frequency (ω) of the MAOS and (ii) relatively higher orientation can be obtained for the combination of γ0and ω, which gives tan δ = 2–3. The lattice constant does not change throughout all the shearing processes and is equal to that before shearing within the experimental errors, indicating that the shear melting does not occur. These results suggest a possibility to control the orientation of the cubic lattice only by changing the conditions of oscillatory shear without using the epitaxial transition from other anisotropic phases, such as the hexagonal and lamellar phases.