Polyclisperse 1,1,1,3,5,5,5-heptamethyltrisiloxane-oligo(propylene oxide-block-ethylene oxide) wetting agents were synthesized through the hydrosilylation of 1,1,1,3,5,5,5-heptamethyltrisiloxane (HMTS) with active hydrogen and allyl oligo(propylene oxide-block-ethylene oxide) [allyl oligo(PO-b-EO)] with hexachloro dihydrogen platinate(IV) as a catalyst. Allyl oligo(PO-b-EO) with a hydrophilic- hydrophobic balance was synthesized through the combination of propylene oxide (PO) and ethylene oxide with allyl alcohol. The wetting agents with a hydrophilic-hydrophobic balance were synthesized. The aqueous solutions of the wetting agents (0.1 wt %) were almost visibly turbid. An increase in the number of hydrophobic groups of HMTS and PO for the wetting agents resulted in a lower critical solution temperature. Lower surface tensions of 20-25 dyn/cm were found above the critical micelle concentration (cmc), and they decreased with an increase in the number of hydrophobic groups. The cmc's were below 0.01 wt %, decreasing with as the number of hydrophobic groups increased. The wetting power and emulsion stability for the oil-in-water systems increased as the concentration of the wetting agents increased, and they decreased as the number of hydrophobic groups increased. (C) 2004 Wiley Periodicals, Inc.