the cold bath hexane was chilled with an fts flexi cool immersion cooler 500 ml round bottom flasks equipped with overhead stirrers were charged with mecl ib ip or bmb the polymerization started with the addition of the alcl 3 catalyst solution which was prepared in advance 0 45 g alcl 3 in 50 g mecl premixed at u2212 30 u00b0 c for 30 min and then cooled down to the reaction temperature after 5 10 min the polymerizations were terminated by the addition of 30 ml prechilled methanol the obtained polymers were purified by being redissolved in hexane precipitated from methanol and dried in a vacuum oven at 40 u00b0 c the final conversions were determined gravimetrically a control butyl polymerization was carried out before the copolymerizations with the brominated monomer the original recipe used for butyl polymerization was changed by reducing the ib amount from 60 g per 200 g total to 20 g to avoid formation multimodal distributions in the resulting polymer the recipe used was as follows ib 20 g ip 0 53 g mecl 179 5 g alcl 3 catalyst solution 2 ml polymer molecular weights and molecular weight distributions were determined by sec with a waters system equipped with six styragel hr columns pore sizes 100 500 10 3 10 4 10 5 and 10 6 u00e5 and thermostated at 35 u00b0 c a dawn dsp 18 angle laser light scattering detector wyatt technology a waters 410 dri detector thermostated to 40 u00b0 c and a waters 996 photodiode array pda detector set at 254 nm thf freshly distilled off cah.