The present invention relates to a composition comprising a hydrophobically modified alkylene oxide urethane polymer with pendant or end-capping tertiary amine groups, the conjugate acids of which have a pK a in the range of about 4.5 to about 6.5. The composition of the present invention is useful as a rheology modifier for paint formulations formulated over a wide pH range and is more stable to heat aging than higher pK a amine-modified HEURs.