Control of micellization induced by disproportionation of 2,2,6,6-tetramethylpiperidine-1-oxyl supported on side chains of a block copolymer

The block copolymer micellization induced by the disproportionation of 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) was performed using acids with different acid strengths. A poly(4-vinylbenzyloxy-TEMPO)-block-polystyrene diblock copolymer (PVTEMPO-b-PSt) produced micelles in 1,4-dioxane by the disproportionation of the TEMPO by HNO₃, HCl, HClO₄, and HSbF₆. The acid strength affected the efficiency of the micellization. The acid/VTEMPO molar ratio required for the micellization decreased with an increase in the acid strength: \( {\text{HNO}}_{\text{3}} < {\text{HCl}} < {\text{HClO}}_{\text{4}} < {\text{HSbF}}_{\text{6}} \). The acid strength also made a difference in the hydrodyamic diameter of the micelles. The stronger acid provided larger micelles. This difference in the micellization was based on the difference in the solubility of the oxoaminium salt formed by the disproportionation of the TEMPO and on the steric hindrance of its counter anion.