Controlling the degree of branching in atom-transfer radical polymerization of hyperbranched polyacrylates

Atom-transfer radical polymerizations of 2-(2-bromopropionyloxy)ethyl acryl ate (BPEA) and 4-(2-bromopropionyloxy)butyl acrylate (BPBA) provided hyperb ranched polyacrylates (HPEA and HPBA, respectively) in this study. The rate of polymerization of BPEA was faster than that of BPBA and the degree of b ranching of HPEA was higher than that of HPBA under the same,reaction condi tions. The degree of branching (DB) of the hyperbranched polyacrylates was enhanced in the presence of acetone or methanol as a cosolvent. In particul ar, the use of acetone resulted in a higher DB than that observed in methan ol by generating the proper reactivity ratio of the two propagating sites.