Anisotropic nucleation and compatibilization of SiO2@PS Janus particles on expandable polystyrene

Inorganic particles usually used as nucleation agent to promote the polymer foaming of supercritical carbon dioxide. However, they are apt to agglomerating in the matrix, which is not conducive to obtaining foamed materials with homogeneous cells. Herein, the organic-inorganic Janus particles possess anisotropic chemical compositions were introduced into expandable polymer, in which two sides can perform compatibilization and nucleation independently. The dispersion of silica@polystyrene (SiO2 @PS) Janus particles (JPs) in PS matrix and the resulting improvements in rheological property, foaming performance, compressive strength of PS was discussed systematically. JPs could be uniformly dispersed in PS matrix attributed to the PS end of JPs. While the SiO2 end of JPs could act as heterogeneous nucleation agent and promote cell formation. Compared with PS foams, PS/JPs foams had smaller and more uniform cell sizes, leading to better compressive properties, i.e. the compressive strength of PS/JPs-5% foams at 100 degrees C, 110 degrees C and 120 degrees C increased by 37.4%, 60.6% and 57.9%, respectively. This work demonstrates that JPs are a novel nucleation and compatibilizer for making polymer foams with optimal cell structure and compressive property.