precipitating into methanol separating the solid polymer from the liquid and drying the polymer in vacuo the polymerization yielded 3 4 grams of polymer a sample taken just before the first styrene addition was characterized to determine the characteristics of the midblock from 1 h nmr spectra the midblock contained 1 8 mol pms with 45 mol bsb triads from gpc analysis m n was 108 600 and the m w m n was 1 4 the final copolymer was also characterized by these techniques from 1 h nmr analysis taking into account the pms incorporation the final copolymer contained 4 0 wt polystyrene gpc analysis gives a m n of 118 400 and an overall m w m n of 1 4 the polymer had no appreciable mechanical strength in a dry box a 5 liter reactor cooled to u2212 90 u00b0 c was charged 18 ml of hexane sodium benzophenone ketal dried and distilled 12 ml of methyl chloride dried by passing the gas through two columns of barium oxide condensing and collecting the liquid in the dry box 56 microliters of dimethylphthalate and 0 13 ml of dimethylaluminum chloride this solution was allowed to age 10 minutes with stirring isobutylene 4 5 ml dried by passing the gas through two columns of barium oxide condensing and collecting the liquid in the dry box along with 0 15 ml of p methylstyrene dried by distillation from calcium hydride was added and dissolved the solution was again allowed to age three minutes separately a stock solution of styrene was prepared by combining 7 1 ml of hexane 4 7 ml of methyl chloride and 8 microliters of dimethylaluminum chloride at u2212 90 u00b0 c and aging.