Analysis of polystyrene surface properties on thin film bonding under carbon dioxide pressure using nanoparticle embedding technique

A gold nanoparticle embedding technique is used to determine how vacuum and pressured carbon dioxide (CO ₂) affect polystyrene (PS) thin film properties. The pressured CO ₂ greatly increased the gold nanoparticle embedding depth, possibly due to a low cohesive energy density near the film surface. For the monodisperse PS used in this study (M _n 1/4 214,000), two spin-coated thin films with intimate contact can be bonded below the bulk glass transition temperature (T _g) under CO ₂ pressure when the embedded depth is larger than half of the gyration radius of PS molecules.