壳层厚度对核-壳结构PS-SiO_2杂化颗粒压缩弹性模量的影响

基于正负电荷间的静电作用制备了具有核-壳结构的聚苯乙烯-氧化硅(PS-SiO2)杂化颗粒,通过调节正硅酸乙酯的用量对样品的SiO2壳层厚度进行控制。利用原子力显微镜(AFM)在微观尺度上测定杂化颗粒的力-位移曲线,根据Hertz接触模型和Sneddon接触模型,考查了SiO2壳层厚度对样品压缩弹性模量的影响。扫描电子显微镜(SEM)和透射电镜(TEM)结果显示,杂化颗粒中PS内核尺寸为(197±9)nm,壳层由SiO2纳米颗粒组成,在本试验范围内杂化颗粒样品的壳厚为11~16nm。在Hertz接触模型条件下,PS微球的弹性模量为(2.2±0.5)GPa,其数值略低于PS块体材料。当SiO2壳厚由11nm增至16nm时,杂化颗粒的弹性模量从(4.4±0.6)GPa增至(10.2±1.1)GPa,其数值明显低于纯SiO2,且更接近于PS内核。

Effect of shell thickness on compressive elastic modulus of core-shell structured PS-SiO2 hybrid particles

The core-shell structured hybrid particles with polystyrene (PS) as the core and SiO₂ nanoparticle as the shell were synthesized via electrostatic interaction based on the opposite charges. The SiO₂ shell thickness of the obtained hybrid particles could be tuned by varying the concentration of tetraethylorthosilicate. The atomic force microscope (AFM) was employed to probe the mechanical properties of the as-prepared samples. The compressive elastic modulus of the sample was measured by analyzing the force curves captured on the particle samples according to the Hertz contact model and Sneddon contact model. As confirmed by scanning electronic microscopy (SEM) and transmission electron microscope (TEM), the size of the PS core is (197±9) nm and the SiO₂ shell which is 11-16 nm in thickness in the test is composed of a lot of tiny particles. Under the condition of Hertz contact model, the elastic modulus of the PS microspheres is (2.2±0.5) GPa. The modulus of the PS-SiO₂ hybrid particle increases with the increase of the thickness of SiO₂ shell. When the shell thickness increases from 11 nm to 16 nm, the elastic modulus of the composite grows from (4.4±0.6) GPa to (10.2±1.1) GPa. The elastic modulus of the composite is much lower than that of the silica, and is more close to the modulus of the PS core.