Polyisobutylene-graft-polystyrene (PIB-g-PSt) was synthesized by quasiliving atom transfer radical polymerization (ATRP) of styrene. The ATRP process was induced by an industrially produced poly-(isobutylene-co-p-methylstyrene-co-p-bromomethylstyrene) macroinitiator (PIF3) in the presence of CuBr and 2,2'-bipyridine. Successful graft polymerizations were performed both in bulk and in xylene solution.Preliminary investigations indicate phase-separated morphology and thermoplastic elastomer (TPE) behavior of this new graft copolymer with certain PIB/PSt ratios. These materials are able to elongate to ca. 500% of their original dimension without any irreversible deformation.

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Friedel–Crafts self‐grafting of polystyrene (PSt) under quasiliving carbocationic polymerization was utilized to develop a new rapid one‐pot method for the preparation of star‐shaped polyisobutylene (PIB). First, the polymerization of isobutylene led to PIB with predetermined molecular weight ($\overline M _{\rm n}$ = 2 000) and narrow molecular weight distribution ($\overline M _{\rm w} /\overline M _{\rm n}$ = 1.03). Then addition of relatively small amount of styrene after isobutylene consumption yielded PIB‐PSt diblocks. Multiple alkylation of the resulting PSt segments by the polystyryl cations led to hyperbranched PSt cores coupling PIB chains to form a star polymer in short reaction time (within an hour) compared to reported methods. The formation of star polymers by this self‐grafting mechanism was proved by gel permeation chromatography equipped with online viscosimeter and 1H NMR spectroscopy.