Effect of solvent on the activation rate parameters for polystyrene and poly(butyl acrylate) macroinitiators in atom transfer radical polymerization

The activation rate parameters of polystyrene (k(act)(S)) and poly(butyl ac rylate) (k(act)(BA)) macroinitiators in ATRP catalyzed by CuBr/4,4'-di-n-he ptyl-2,2'-bipyridine have been determined at 110 degrees C using a combinat ion of nitroxide exchange reactions with HPLC analysis. The method is based on exchange of the bromide end group with a hydroxy-TEMPO end group. The d epletion of the macroinitiator is monitored as a function of time. The meth od :is applicable in different, solvents, which implies the possibility to investigate the effect of solvent characteristics. Solvent polarity has a n egative influence on k(act)(S) and a positive effect on k(act)(BA). The abi lity of the solvent to act as ligand in the copper complex hampers the acti vation process for both macroinitiators, while the presence of hydroxy grou ps in the solvent increases both activation rate parameters.