Synthesis of silica particles grafted with poly(ionic liquid) and their nucleation effect on microcellular foaming of polystyrene using supercritical carbon dioxide

We present the synthesis and characterization of silica particles modified by a poly(ionic liquid), namely, poly[2-(methacryloyloxy)ethyl]trimethylammonium tetrafluoroborate (P[MATMA][BF4]), which has a strong carbon dioxide absorption, and its application as a nucleation agent in polymer foaming. Silica particles with different particle sizes were fabricated by the sol–gel method and then grafted with (P[MATMA][BF4]) brushes by surface-initiated atom-transfer radical polymerization. The modified silica particles (SiO2P[MATMA][BF4]) were introduced into a polystyrene matrix by solution blending. The (P[MATMA][BF4]) brushes grafted onto the silica particles were able to slightly increase the carbon dioxide solubility, and consequently, SiO2P[MATMA][BF4] showed a higher heterogeneous nucleation efficiency in the foaming process compared to amino-functionalized silica particles (SiO2NH2) used as control.