Effect of drying method on the structure and porous texture of silica-polybutadiene hybrid gels: Supercritical vs. ambient pressure drying

Drying methods can strongly affect the structure, pore size and morphology of organic-inorganic aerogels. In this study, the textural properties of silica-polybutadiene hybrid gels which were dried in supercritical condition (aerogels) were compared with those dried in ambient pressure condition (xerogels). The silica-polybutadiene wet gels were synthesized by two-step sol-gel process using different amounts of silane functionalized polybutadiene latex nanoparticles (0, 10, 30 and 50 wt.%). In order to decrease the surface tensions in silica pore network, the resulting gels were modified with hexamethyldisilazane (HMDZ) before drying. Nonetheless, high volume loss was observed in ambient pressure drying. The supercritical dried aerogels indicated lower density ranged from 0.08 to 0.24 g/cm3 and higher porosity from 96.1 to 79.6% comprised to those dried in ambient pressure condition. Supercritical drying could avoid polymer particles aggregation, leading to a wider pore distribution including larger pores and higher pore volumes (ranging from 4.38 to 1.48 m3/g). Moreover, a different non-rigid structure was found from nitrogen sorption isotherms in supercritical condition.