The oxidation of PSar was performed according to the procedure described . PSar (0.142 g, 0.0596 mmol, 1.0 eq.) was dissolved in 5 mL dry DCM and cooled to 0°C in an ice bath. m-CPBA (0.021 g 0.119 mmol, 2.0 eq.) was dissolved in 3 mL DCM, added dropwise to the polymer solution and stirred for 3.0 -5.0 h while warming to room temperature. The resulting polymer was twice precipitated from cold diethyl ether and dried under vacuum with the following dissolution in water and lyophilization to give the white powder (0.128 g, 89 %).