Nitroxide‐Mediated Radical Dispersion Polymerization of Styrene in Supercritical Carbon Dioxide Using a Poly(dimethylsiloxane‐ block ‐styrene) Alkoxyamine as Initiator and Stabilizer

Summary: Nitroxide‐mediated dispersion polymerization of styrene in supercritical carbon dioxide has been performed successfully at 110 °C using a new polymeric so‐called inistab species, which fulfils the dual functions of an initiator and a colloidal stabilizer. The inistab species comprised a poly(dimethylsiloxane) block and a polystyrene block end‐capped with the nitroxide N ‐ tert ‐ N‐ butyl‐ N ‐[1‐diethylphosphono‐(2,2‐dimethylpropyl)] nitroxide (SG1). The dispersion polymerization resulted in sub‐micron sized polymer particles and polymers of narrow polydispersity.TEM micrograph of PS particles prepared in the dispersion polymerization of S in scCO 2 in the presence of PDMS( \overline M _{\rm n}  = 6 500)‐ b ‐PS( \overline M _{\rm n}  = 4 500)‐SG1 at 110 °C.