Abstract
After briefly reviewing some preparation schemes of porous polymeric materials, polymer foaming methods which use supercritical carbon dioxide (CO_2) or nitrogen (N_2) as a physical blowing agent are brought into focus. Microcellular foams whose cell size is less than 10 μm and cell density is higher than 10^8 cm^<-3> are prepared by the method. Controllability of cell morphology in the foaming method is discussed. Several schemes of reducing the cell size to nanometer scale and producing nanocellular foam are introduced. The use of crystal nucleating agent as bubble nucleating agent is also introduced as a promising method for producing micro/nanocellular foam.
