Cationic Block and Graft Polymerization of 1,3-Dioxolane onto Living Poly(p-methoxystyrene)

Cationic block and/or graft copolymerization of 1,3-dioxolane (DOL) onto poly(p-methoxystyrene) [poly(p-MOS)] was investigated. Block copolymer were obtained by the polymerization of DOL initiated with living poly(p-MOS) prepared with an iodine initiator in carbon tetrachloride at 0∼−15°C. The successful block copolymerization required the presence of a neutral salt with a less nucleophilic counterion (ClO4⊖, BF4⊖, or SbF6⊖), which activates the living end via counterion exchange; in the absence of the salt, the living poly(p-MOS) could not polymerize DOL. The blocking reactions were accompanied by the formation of graft copolymers due to the attack of the propagating poly(DOL) chains onto the aromatic rings of poly(p-MOS). The ClO4⊖ anion functioned as the best counterion, leading to higher yields of the block copolymer with less graft copolymers. p-MOS–DOL graft copolymers were also prepared by the DOL polymerization with an acetyl salt, (AcX; X=ClO4⊖, BF4⊖, SbF6⊖), in the presence of a dead poly(p-MOS).