Application of nitroxide-terminated polymers prepared by sonochemical degradation in the synthesis of block copolymers

The ultrasonic irradiation of a polymer solution results in the breakage of macromolecular C-C bonds. In the presence of radical scavengers the formed macroradicals are prevented from termination reactions as combination or disproportionation. Using nitroxides as trapping agents the polymer is transformed into a macroinitiator, which can be used in controlled free-radical polymerization to synthesize block copolymers. In this work several polymers were exposed to sonochemical degradation and terminated with various nitroxides. e.g. OH-TEMPO and TIPNO. In a second reaction step the prepared polymer-nitroxide-adducts were applied as macroinitiators in controlled free-radical polymerizations with styrene. The obtained products were mixtures of block copolymer and the corresponding homopolymers. The visco-elastic properties were investigated by rheological analysis. A special separation technique with selective solvents was applied to determine the content of block copolymer. Synthesis of block copolymers with sonochemically prepared macroinitiators.