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 degrees 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-(M) over bar (n) PS, the temperature was lowered. At 90 degrees C, the use of BlocBuilder yielded PS of (M) over bar (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 degrees C. Since these nitroxides were too constrained, the decrease in k(c) caused a loss of control and livingness for high-(M) over bar (n) polymers.