Synthesis of polypropylene graft copolymers by the combination of a polypropylene copolymer containing pendant vinylbenzene groups and atom transfer radical polymerization

This article discusses a facile and inexpensive reaction process for preparing polypropylene-based graft copolymers containing an isotactic polypropylene (i-PP) main chain and several functional polymer side chains. The chemistry involves an i-PP polymer precursor containing several pendant vinylbenzene groups, which is prepared through the Ziegler-Natta copolymerization of propylene and 1,4-divinylbenzene mediated by an isospecific MgCl ₂$-supported TiCl ₄ catalyst. The selective monoenchainment of 1,4-divinylbenzene comonomers results in pendant vinylbenzene groups quantitatively transformed into benzyl halides by hydrochlorination. In the presence of CuCl/pentamethyldiethylenetriamine, the in situ formed, multifunctional, polymeric atom transfer radical polymerization initiators carry out graft-from polymerization through controlled radical polymerization. Some i-PP-based graft copolymers, including poly(propylene-g-methyl methacrylate) and poly(propylene-g-styrene), have been prepared with controlled compositions.