Nanocellular CO2 foaming of PMMA assisted by block copolymer nanostructuration

•We obtain nanocellular foams by different nucleation mechanisms.•We study the micelles present on PMMA/MAM blends.•We found a clear relationship between the initial micelles and the final cells.•We control the nucleation process with a self-assembled nanostructuration. Polymer foams with closed cells in the range of 90–200nm and relative densities between 0.4 and 0.6 have been produced by CO2 gas dissolution foaming from neat poly(methyl methacrylate) (PMMA) and blends of PMMA and a triblock copolymer [poly(methyl methacrylate)-block poly(butyl acrylate)-block poly(methyl methacrylate), MAM]. Foams produced from these PMMA/MAM blends present a clear heterogeneous nucleation mechanism showing a clear relationship between the nanostructuration of the solid blend precursors and the nucleation efficiency of block copolymers during the saturation–expansion process. This paper discusses the role of the nanostructuration pattern of PMMA/MAM blends on the cells nucleation mechanism, showing that nucleation takes place preferably on the MAM nanostructures due to a combination of their high CO2-philicity, surface tension and morphology.