Porous films prepared from poly (styrene-co-acrylonitrile)/dichloromethane system via evaporation induced phase separation: Structure - thermodynamic aspects

Abstract

SAN porous films were prepared for the first time by the evaporation-induced phase separation (EIPS, dry casting) process using dichloromethane (DCM) as solvent and 2-propanol (Pr) and polyethylene glycol 400 (PEG400) as nonsolvent. The effects of nonsolvent type and its concentration, the mixture of nonsolvents, and polymer concentration on the structure of porous films were investigated. By changing the composition of the solution, films with an average pore diameter of 0.9–3.5 μm and porosity of up to 52% were obtained. To elucidate the process, the phase diagram of the systems was drawn experimentally and theoretically. The approaching ratio of solution (ARSolution) and the nonsolvent efficiency for creating pores (EfNS) were also introduced. As the initial solution composition approached the two-phase region (increasing ARSolution), porosity and EfNS increased. EfNS of 2-propanol was lower than PEG, but at high ARSolution, their EfNS became similar.