Graded foams by time-dependent boundary conditions in blowing agent sorption

Layered and graded foams have proven superior to their uniform counterparts in terms of structural, and functional properties. This is also suggested by nature, which is abundant with porous material structures whose attributes go far beyond any artificial foam. To date, advanced foamed structures have been generated via advanced, though complex/time consuming technologies. We have explored the possibility of generating layered and graded polymeric foams by using simple gas foaming technology, with the sole introduction of time-varying boundary conditions of the gas sorption stage. We show that by ingeniously designing the sorption step it is possible to achieve nontrivial gas concentration profiles and, correspondingly, at pressure release, foams with density and/or morphology profiles.