Differential scanning calorimetry has been used to investigate the effect of pH upon the temperature interval over which aggregation occurs in aqueous solutions of the ethylene oxide (EO)/propylene oxide (PO) block co-polymeric compound tetronic T701 (molecular formula (EO4PO13)(2)NCH2CH2N(PO13EO4)(2)). Self association, in this system, occurs at elevated temperatures because the PO blocks become increasingly non-polar and, as a consequence, self associate because of the hydrophobic effect. pH titration shows that the central ethylene diamine moiety is di-basic with pK(a) values of 3.8 and 8. Thus, in aqueous solution when the pH value is below 8 a necessary pre-condition for self association is deprotonation. A theoretical model is developed-based upon this hypothesis-which attempts to replicate, with some success, the effect of pH upon the calorimetrically observed T701 self association process. (C) 2003 Elsevier B.V. All rights reserved.