Cosolvent effect on the aggregation of amphipathic highly branched diblock polyether in aqueous solution.

An amphipathic highly branched diblock polyether, PA60-2-40, was synthesized via anion ring-opening polymerization of propylene oxide (PO) and ethylene oxide (EO), using phenol-amine resin (PA) as the initiator. The molecular structure was confirmed by FT-IR and ¹H NMR. The surface tension and fluorescence spectroscopy measurements provide information about the effect of cosolvents on the critical micelle concentration (CMC) and the standard Gibbs energy (ΔG ^o_mic). The cosolvents have a significant effect on the CMC of PA60-2-40; the CMC first decreases and then increases with increasing content of n-pentanol, but with an increase of ethylene glycol concentration, there is durative decrease of the CMC. The micellization becomes more spontaneous in the presence of cosolvents with more hydroxyl groups, but the CMC does not monotonically increase or decrease with the increasing carbon chain length of aliphatic monohydric alcohols. The values of surface activity parameters (Г _max, A _min and ∆G ^o_mic) calculated all coincide with the results of the experiment. Additionally, TEM and DLS demonstrate that the size of the micelles can be changed by the addition of alcohols, but the aggregation morphology will not change. [ABSTRACT FROM AUTHOR]