Aggregation Behavior of Amphiphilic Dendritic Block Copolymer with Butanediyl-α,ω-bis(tetradecyldimethylammonium bromide) in Aqueous Solution

Abstract

Aggregation behavior of an amphiphilic dendritic block copolymer, a generation 1.0 poly(amidoamine) (G1.0 PAMAM) dendrimer based poly(propylene oxide) (PPO)-block-poly(ethylene oxide) (PEO) copolymer that was abbreviated as PPP, with a cationic gemini surfactant butanediyl-α,ω-bis(tetradecyldimethylammonium bromide) (14-4-14) in aqueous solution was investigated by the measurements of steady-state fluorescence (FL), cloud point (CP), transmission electron microscope (TEM), and dynamic light scattering (DLS). Through FL method, the critical aggregation concentration (CAC) of PPP in the absence and presence of 14-4-14 was determined. As the concentration of 14-4-14 increases, CAC values increase, suggesting the participation of copolymer−surfactant complexes in aggregate formation. The CP temperature of PPP increases as the content of 14-4-14 increases in the mixed system, which indicates that 14-4-14 increases the solubility of PPP. From TEM and DLS, the morphology and size distribution of the aggregates were obtained. The spherical aggregates are found to be larger in size and narrower in distribution with the addition of 14-4-14, which confirms further the formation of mixed aggregates. All of the above are explained on the basis of strong interactions between PPP and 14-4-14. Through hydrophobic interactions, 14-4-14 molecules can associate with PPP molecules to form copolymer−surfactant complexes that can aggregate further.