Polymerization-induced self-assembly based on ATRP in supercritical carbon dioxide

Abstract

Polymerization-induced self-assembly (PISA) based on atom transfer radical polymerization (ATRP) has been performed in supercritical carbon dioxide (scCO₂) using a bromo-terminated poly(dimethylsiloxane) (PDMS-Br) species as the macroinitiator (the solvophilic first block) and poly(benzyl methacrylate) as the solvophobic second block. The polymerizations proceeded to high conversions with good control/livingness. Transmission electron microscopy revealed the formation of the first higher order morphologies in scCO₂, namely worms and likely vesicles. Interestingly, a highly regular microphase separated multilayered morphology was also observed, which was not observed with PISA carried out in conventional solvents. Overall, the morphologies formed cannot be rationalized based on simple considerations of the relative block lengths and packing parameters, as is typically the case in dispersion PISA in common solvents such as water and water/alcohol. Seemingly, the unique properties of scCO₂ lead to different polymer domains.