Synthesis of ABCD-Type miktoarm star copolymers and transformation into Zwitterionic star copolymers

ABCD-type 4-miktoarm star copolymers of styrene (St), a-methylstyrene (alpha MSt), tert-butyl methacrylate (tBuMA), and 4-vinylpyridine (4VP) were synthesized via anionic polymerization using 1,3-bis(l-phenylvinyl)benzene (m-DDPE) as the linking molecule. The synthetic route was rationally designed with respect to the reactivity of individual propagating anion towards the double bond of m-DDPE. Thus the synthesis includes several consecutive key reactions, for example, the monoaddition of polystyryllithium towards m-DDPE, the polymerization of tBuMA initiated by the resulting monoadduct to produce a diblock macromonomer, the coupling of the macromonomer with poly(alpha-methylstyryl)lithium to form a 3-arm star anion, and the polymerization of 4-vinylpyridine initiated by the star anion. These reactions were conducted either in a one-pot process, in which the diblock macromonomer was in situ coupled with poly(alpha-methylstyryl)lithium, or in a batch polymerization process, in which the same diblock macromonomer was separated. The final product was hydrolyzed to produce a zwitterionic miktoarm star copolymer, which was soluble at lower pH but insoluble in neutral and basic solution. (c) 2007 Wiley Periodicals, Inc.