Hyperbranched Copolymerization . A typical polymerization procedure was as follows . Cp 2 TiCl 2 ( 25 mg , 0.1 × 10 -3 M ) , Zn ( 7 mg , 0.1 × 10 -3 M ) and dioxane ( 0.5 mL ) were added into a 5 mL glass tube , and then the reaction solution was degassed using three freeze-vacuum-thaw cycles , and reacted at room temperature for 10 min , until the solution turned lime green . GMA ( 0.355 g , 2.5 × 10 -3 M ) , St ( 0.260 g , 2.5 × 10 -3 M ) , CuBr 2 ( 23 mg , 0.1 × 10 -3 M ) and bpy ( 48 mg , 0.3 × 10 -3 M ) were added into the reaction solution , and the tube was again degassed using three freeze-vacuum-thaw cycles . The tube was then sealed under a vacuum , and the sealed tube was immersed in an oil bath at 90 °C . After polymerization for 4 h , the tube was rapidly cooled to room temperature . The polymer solution in THF was passed through a short column of neutral alumina to remove the metal salt . After two precipitations by addition of the polymer solution into petroleum ether ( 30- 60 °C ) , the hyperbranched P(GMA - co -St ) -Br n ( HP(GMA-St)-Br n ) was obtained in a 51 % yield after filtration and drying in a vacuum oven at 30 °C overnight . The monomer conversion was determined gravimetrically . was 78 000 and was 1.19 .