Emergence of Strong Nonlinear Viscoelastic Response of Semifluorinated Alkane Monolayers.
Emergence of Strong Nonlinear Viscoelastic Response of Semifluorinated Alkane Monolayers.
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半氟化烷烃单层的强非线性粘弹性响应的出现
DOI：
10.1021/acs.langmuir.7b03997
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发表时间：
2018
期刊：
影响因子：
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通讯作者：
M. Tanaka
中科院分区：
文献类型：
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作者：
S. Mielke;T. Habe;M. Veschgini;X. Liu;K. Yoshikawa;M.P. Krafft;M. Tanaka
用界面扩张流变学方法研究了氟碳/碳氢四嵌段两亲分子二（FnHm）（（CnF 2n +1CH 2）（Cm-2 H2 m-3）CH-CH（CnF 2n +1CH 2）（Cm-2 H2 m-3））单分子膜的粘弹性.由于响应函数的频散表明di（FnHm）在界面处形成二维凝胶，因此首先用经典的Kelvin-Voigt模型分析了di（FnHm）的粘度和弹性。然而，应力响应函数的整体形状清楚地表明，即使在非常低的表面压力（π = 5 mN/m）和小应变振幅（u 0 = 1%）的非线性的出现。高次谐波的傅立叶变换响应函数表现出明显的增加，只有从奇模的强度，对应于反射下的非线性弹性分量，因为镜像对称。强非线性粘弹性的二（FnHm）在低表面压力和应变振幅的出现是非常独特的相比，其他表面活性剂系统的非线性粘弹性先前报道的，这表明一个大的潜力，这样的氟碳/烃分子使用的自组装域的小分子调制界面的力学。
Viscoelasticity of monolayers of fluorocarbon/hydrocarbon tetrablock amphiphiles di(FnHm) ((CnF2n+1CH2)(Cm–2H2m–3)CH–CH(CnF2n+1CH2)(Cm–2H2m–3)) was characterized by interfacial dilational rheology under periodic oscillation of the moving barriers at the air/water interface. Because the frequency dispersion of the response function indicated that di(FnHm) form two-dimensional gels at the interface, the viscosity and elasticity of di(FnHm) were first analyzed with the classical Kelvin–Voigt model. However, the global shape of stress response functions clearly indicated the emergence of a nonlinearity even at very low surface pressures (π ≈ 5 mN/m) and small strain amplitudes (u0= 1%). The Fourier-transformed response function of higher harmonics exhibited a clear increase in the intensity only from odd modes, corresponding to the nonlinear elastic component under reflection because of mirror symmetry. The emergence of strong nonlinear viscoelasticity of di(FnHm) at low surface pressures and strain amplitudes is highly unique compared to the nonlinear viscoelasticity of other surfactant systems reported previously, suggesting a large potential of such fluorocarbon/hydrocarbon molecules to modulate the mechanics of interfaces using the self-assembled domains of small molecules.