Surface properties and aggregation behaviors of amphiphilic highly-branched block polyethers in aqueous solution

A series of new highly-branched block polyethers, PA-PO-EO, were synthesized via anion ring-opening polymerization of propylene oxide (PO) and ethylene oxide (EO), using phenol-amine resin (PA) as the initiator. The molecular structures were confirmed by end group analysis, FT-IR and ¹H NMR. The surface properties and self-assembly behaviors in aqueous solution were investigated by surface tension, fluorescence spectroscopy, UV–vis spectra and TEM. The results indicated that the CMC of polyethers aqueous solution presented a wide range, and the scope of CMC corresponded to the content of EO. Moreover, the proportion of PA had a great effect on the properties of the whole polymer molecules, and the number of blocks was a critical factor to the process of self-assembly. A corresponding critical size of the spherical micelles formed by different samples was presented from TEM photographs. Accordingly, the possible self-assembly mechanisms were put forward to explain the formation of all kinds of aggregates. In a word, the PA and PPO blocks aggregated to form a relatively hydrophobic core, which was stabilized by a hydrophilic PEO corona.