用AFM力曲线技术测定聚合物微球的压缩杨氏模量

Measurement of Compressive Young's Modulus of Polymer Particles Using Atomic Force Microscopy

用无皂乳液聚合法制备了粒径为200-500nm的单分散聚苯乙烯(PS)微球。依靠正负电荷间作用力将样品分散在经过亲水处理的硅热氧化片刚性衬底上,借助原子力显微镜纳米压痕技术测定了PS颗粒样品的力学性质;依据样品的力-位移曲线,根据弹性力学接触模型,计算出PS微球样品的压缩杨氏模量为2-3 GPa(Hertz模型)和2-6 GPa(Sneddon模型)。结果表明,微球样品的杨氏模量计算值略低于PS块体材料,且随着粒径的增加而缓慢增大。Hertz模型更适于计算本文制备的亚微米级PS微球的压缩杨氏模量。

The monodispersed polystyrene(PS) particles with the size of 200-500 nm were prepared via a soap-free emulsion polymerization method. The as-synthesized PS microspheres were immobilized on a rigid substrate surface through the attraction between the negative-charged silica and the positivecharged PS. The mechanical properties of the as- synthesized PS microspheres were measured by a Peak Force tapping atomic force microscope. The compressive Young's moduli(E) of 2-3 GPa(Hertz's model) and 2-6 GPa(Sneddon's model) were calculated by the analysis of the force-displacement curves captured on the top of the PS particles. The moduli were slightly less than that of PS bulk materials, and the E values increased slowly with an increase of the size of the PS particles. In addition, the Hertz's model might be more suitable to calculate the E of the obtained samples than the Sneddon's model.