Nanocellular foaming of fluorine containing block copolymers in carbon dioxide: the role of glass transition in carbon dioxide

Abstract

Carbon dioxide foaming in polymeric materials has been recognized as an environmentally friendly method to introduce microfoam consisting of cells of micrometre size (microcells). Our group has demonstrated that CO₂-philic fluorinated block domains of block copolymers worked as nuclei of foams and further decreased the size of cells to around 10 nm (nanocells). In this study, we introduced nanocells to poly[(methyl methacrylate)-b-(perfluorooctylethyl methacrylate)] (PMMA–PFMA, MF) and poly[(perfluorooctylethyl methacrylate)-b-(methyl methacrylate)-b-(perfluorooctylethyl methacrylate)] (PFMA–PMMA–PFMA, FMF), and compared the resultant porosity with those of polystyrene-based fluorinated block copolymers previously studied. The temperature providing a maximum porosity for the PMMA based copolymers was lower than that for the PS based copolymers. We further measured the glass transition temperatures, T_g, of skeleton blocks, i.e. PS and PMMA, in the presence of CO₂ using a quartz crystal resonator and revealed that the temperature of maximum porosity is correlated to the decreased T_g of the skeleton polymers in CO₂.