A Step Towards High-Molecular-Weight Living/Controlled Polystyrene Using SG1-Mediated Polymerization

The synthesis of high‐molecular‐weight living/controlled polystyrene by NMP was studied. The combination of Ac2O and alkoxyamines based on nitroxides TEMPO, TIPNO, and SG1 was tested at 130 °C. With TEMPO and TIPNO, dipole/dipole interactions led to a decrease in nitroxide concentration and an acceleration of the reaction. To minimize thermal auto‐initiation and thus obtain high‐$\overline M _{\rm n}$ PS, the temperature was lowered. At 90 °C, the use of BlocBuilder yielded PS of $\overline M _{\rm n}$ = 210 000 g · mol−1 with a living fraction of 60%. Finally, new SG1‐based nitroxides were used to perform the polymerization at 75 °C. Since these nitroxides were too constrained, the decrease in kc caused a loss of control and livingness for high‐$\overline M _{\rm n}$ polymers. The synthesis of high‐$\overline M_{\rm n}$ living/controlled PS by SG1‐NMP was investigated. The use of acetic anhydride as additive was tested and the mechanism of acceleration investigated. In all cases the results were not conclusive. The temperature was then decreased. First new SG1‐based nitroxides have been used to perform the polymerization at 75 °C. Since these nitroxides were too constrained, the decrease in kc caused the loss of control. Finally high‐$\overline M _{\rm n}$ and living PS was prepared at 90 °C thanks to the BlocBuilder alkoxyamine.