Synthesis, characterization, and properties of block and bigraft copolymers

The syntheses of poly(styrene‐b‐isobutylene), poly[(ethylene‐co‐propylene‐co‐1,4‐hexadiene)‐g‐styrene‐g‐α‐methylstyrene], and poly[(ethylene‐co‐propylene‐co‐1,4‐hexadiene)‐g‐styrene‐g‐isobutylene] have been accomplished by using the principle of selective sequential initiation. This method makes use of the large differences in initiation rates that exist between labile organic chlorides and bromides when these halides interact with alkylaluminum compounds. Synthesis conditions have been worked out which allow composition control. These new AB blocks and bigrafts exhibit unusual mechanical and solubility properties, some of which will be described. For example, the Nordel‐g‐PSt‐g‐PIB bigraft exhibits only one low temperature transition (DSC, Rheovibron), suggesting an intimate aggregation of Nordel and polyisobutylene phases.