pH adjusted thickener system

The present invention relates to a composition having a pH-dependent viscosity, comprising (A) at least one surfactant of the general formula (I) are: (R1 - [(O- (CH2) 2) x1 (O-CH ( CH3) CH2) x2] O) kP (= O) (OH) 3-k (I), wherein the order of alkyleneoxy units is arbitrary, R1 is selected from linear or branched C12-C22 alkyl, C12- C22 alkenyl, C12-C22 alkynyl group, (C11-C21 alkyl) carbonyl, (C11-C21 alkenyl) carbonyl, and (C11-C21 alkynyl) carbonyl, k is 1 or 2, and x1 and x2 independently an integer of 0-20, the sum of X1 and x2 is a number from 1 to 20, and (B) at least one hydrophobic group comprising at least two interconnected via a bridging hydrophilic group (α) R2 is thickener. The present invention also relates to the use thereof in a controlled adjustment of the rheological properties of aqueous compositions and to a method of treating a subterranean geological formation.