pH responsive heteroarm starlike micelles from double hydrophilic ABC terpolymer with ampholitic A and C blocks

We report on the phase behavior and micellization phenomena of a poly(2-vinylpyridineb-poly(methyl methaerylate)-b-(poly(acrylic acid) block terpolymer (P2VP-PMMA-PAA) in aqueous dilute solutions. This double hydrophilic terpolymer exhibits different self-assemblies depending on the pH of the solution. At low pH (1-2) heteroarm starlike micelles are formed bearing interactive P2VP and PAA arms in the corona. Aging phenomena due to intramicelleral interactions lead to morphology changes from Janus (segregated arms) to shell cross-linked micelles (mixed arms). As the pH increases from 2 to 3, electrostatic intermicellar attractive interactions rise leading to the formation of nonregular aggregates. An insoluble two-phase region around the isoelectric point of the ampholitic chains was observed between pH 3.2 and 5.8. Finally, at higher pH, an unexpected probably out-of-equilibrium morphology of aggregated amphiphilic heteroarm starlike micelles was observed after deposition on the mica substrate.