Nanoaggregates of ABC-type triple hydrophilic block copolymers by binding of cationic surfactant

A triple hydrophilic block copolymer comprised of poly(ethylene oxide), poly(sodium 2-acrylamido-2-methylpropanesulfonate), and poly(methacrylic acid) (PEO–PAMPS–PMAA) does not form a micelle by itself when it is dissolved in water. However, in the previous paper, we fabricated the nanoaggregates of PEO–PAMPS–PMAA and cationic surfactant, such as cetyltrimethylammonium chloride (CTAC), by insolubilizing the anionic PAMPS and/or PMAA blocks of the polymer with CTAC only at high pH. In this paper, we fabricated the nanoaggregates of dodecyltrimethylammonium chloride (DTAC) and PEO–PAMPS–PMAA in a wide range of pH to examine the effect of ionization of the PMAA blocks of the polymer on the aggregates formation of PEO–PAMPS–PMAA. The properties of the nanoaggregates are affected by the ionization of PMAA block of the polymer. DTAC (C12 alkyl chain) was employed instead of CTAC (C16 alkyl chain) to reveal the effect of alkyl chain length of surfactant on the aggregate formation of PEO–PAMPS–PMAA. The properties of PEO–PAMPS–PMAA nanoaggregates also depend on the structure of surfactant. The binding of DTAC to PEO–PAMPS–PMAA was monitored by electrophoresis measurements, while the formation of DTAC/PEO–PAMPS–PMAA nanoaggregates was confirmed by scanning electron microscopy, dynamic light scattering measurements and fluorescence spectroscopy.