Influence of Line Tension on Spherical Colloidal Particles at Liquid-Vapor Interfaces

Atomic force microscopy (AFM) imaging of isolated submicron dodecyltrichlorosilane coated silica spheres, immobilized at the liquid polystyrene- (PS-) air interface at the PS glass transition temperature, T₆, allows for determination of the contact angle versus particle radius R. At T₆, all versus R measurements are well described by the modified Young's equation for a line tension =0. 93 nN. The AFM measurements are also consistent with a minimum contact angle ₌₈₍ and minimum radius R₌₈₍, below which single isolated silica spheres cannot exist at the PS-air interface.