The phase equilibria and surface tension of a polypropylene polyol (PPP) series was studied in aqueous solvent systems. The PPP series was composed of ethylene oxide (K) and propylene oxide (PO) groups, exhibiting specific interactions with both water and alcohols. Binary and ternary liquid-liquid equilibria (LLE) of the PPP series were determined via thermo-optical analysis (TOA) methods, which represented closed-loop miscibility in water and Treybal Type 1 behavior in water and methanol (MeOH), respectively. The surface tension of the ternary PPP1/water/MeOH system was measured using a well-known plate method. The dendritic characteristics of the PPP series were reflected through modeling using lattice cluster theory (LCT) for complex structures of the polymer. The phase diagrams and surface tension of the PPP series were described from binary to ternary systems based on LCT incorporated with Guggenheim's treatment using predetermined parameters. The calculated results of both systems were in good agreement with the experimental data using the same interaction energy parameters. (C) 2018 Elsevier Ltd. All rights reserved.