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Si02纳米颗粒单层膜流变特性的双Wilhelmy片法研究
Rheological study of silica nanoparticle monolayers via two orthogonal Wilhelmy plates
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摘要: 本文采用两个互相垂直的Wilhelmy片对不同润湿性的SiO：纳米颗粒单层膜的表面压和黏弹性进行了研究，并利用Brewster角显微镜（BAM）对单层膜的形貌演变进行了观测．实验发现，当水面完全被颗粒覆盖时，单层膜的表面压具有明显的各向异性，中等润湿性（34％SiOH）的颗粒膜其表面压各向异性最大．压缩模量E和剪切模量G均在中等润湿性时出现最大值．这些结果表明，单层膜的流变性能与泡沫的稳定性密切相关．疏水性最强（20％SiOH）的颗粒膜具有形状记忆效应，这可能是纳米颗粒在受压过程中发生了不可逆聚集以及单层膜内应力驱使纳米颗粒进行位置调整造成的．Abstract: We investigate the rheological properties of silica nanoparticle monolayers at the air-water interface by using two orthogonal Wilhelmy plates in the Langmuir trough and Brewster angle microscopy （BAM）. Remarkable anisotropic effect of surface pressure is observed when the layers are fully covered by particles. The pressure anisotropy is the most prominent for the layer of particles with 34% SiOH on their surface. The elastic compression and the shear moduli present the maxima at intermediate hydrophobicity. The dependence of rheological properties on particle hydrophobicity is closely related to the foamability and the stability of the foams made from these particle dispersions. A shape memory effect is observed in the condensed layer of the most hydrophobic particle （20% SiOH ）, which may result from the irreversible organization of particles and the particle arrangement driven by the inner stress stored in the layer.
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