Controlled free radical polymerization of styrene initiated by a [BPO-polystyrene-(4-acetamido-TEMPO)] macroinitiator

Abstract

The bulk polymerization of styrene at 125°C was studied using a [BPO‐polystyrene‐(4‐acetamido‐TEMPO)] macroinitiator synthesized by a styrene polymerization in the presence of 4‐acetamido‐2,2,6,6‐tetramethylpiperidine‐N‐oxyl (4‐acetamido‐TEMPO) and benzoyl peroxide (BPO). The rates of polymerization were independent of the initial macroinitiator concentration and they were very similar to that for the thermal autopolymerization of styrene. Additionally, different types of N‐oxyls did not have any effect on the polymerization rate. The number‐average molecular weights (Mn) of the obtained polymers agreed very well with theoretical predictions, deviations were observed only at low macroinitiator concentrations. Increasing macroinitiator concentrations resulted in lower magnitudes of the growing molecular weights and reduced polydispersities (Mw/Mn) at the initial stage of the polymerization. The concentration of the polymer chains was calculated, and it was recognized that the concentration of polymer chains increased during the polymerization as a result of an additional radical formation due to the thermal self‐initiation of styrene. This thermal self‐initiation could be proved qualitatively by the addition of N‐oxyl to a macroinitiator polymerization system.

Thermal self‐initiation of styrene in the presence of TEMPO radicals: Bulk and miniemulsion

“…This would indicate that TEMPO is playing a role as an initiator to start a propagating polymer chain. Although there are some more supporting results of this mechanism reported,27 the Mayo mechanism is still frequently applied in the styrene thermal self‐initiation in the presence of TEMPO radicals 28–32. TEMPO radicals can abstract the weakly bonded hydrogen atom from a styrene dimer and form a dimer radical and a hydroxylamine 33.…”

Kinetics of Cap Separation in Nitroxide-Regulated “Living” Free Radical Polymerization: Application of a Novel Methodology Involving a Prefluorescent Nitroxide Switch

“…The average molecular weight ( M w ) was 16 780, with a polydispersity of 1.23. This low polydispersity is typical of the LFRP method employed for the polymerization of styrene. ,, …”

“…This low polydispersity is typical of the LFRP method employed for the polymerization of styrene. 2,10,11 Temperature Dependence. The thermal studies were carried out by adding an excess (1.5 × 10 -4 M) of the prefluorescent probe to a chlorobenzene solution of polystyrene (1.5 × 10 -6 M) prepared by LFRP and end-capped with TEMPO.…”

Nitroxide-Mediated Living Free Radical Miniemulsion Polymerization of Styrene

“…Living/controlled free radical polymerizations are typically divided into three categories: stable free radical polymerization (SFRP), atom transfer radical polymerization (ATRP), and reversible addition fragmentation chain transfer polymerization (RAFT). SFRP in bulk systems has been thoroughly studied. − However, comparatively little has been reported using this technique in emulsion polymerization , or dispersion polymerization …”

“…SFRP in bulk systems has been thoroughly studied. [3][4][5][6][7][8][9][10][11][12] However, comparatively little has been reported using this technique in emulsion polymerization 13,14 or dispersion polymerization. 15 This article will focus on the application of the SFRP technique in miniemulsion polymerizations.…”