Production of cellular polymers without solid outer skins by gas dissolution foaming: A long-sought step towards new applications

•Innovative design for producing skinless polymer foams by gas dissolution foaming.•The gas diffusion barrier maintains high gas concentration in the polymer edges.•Achievement of skinless polymer foams by using the gas diffusion barrier approach.•Thin films with homogenous structures were completely foamed without solid skins.•Porous in the outer layers expose the inner cellular structure to external medium.