Through the macromolecule reaction method, a series of 4-isopropylbenzyl chloride (IPBC) hydrophobically-modified hydroxyethyl cellulose (HAHEC) were synthesized. The use of suitable amount of hydrophobic monomer can ensure both the strong intermolecular association and good water-solubility of HAHEC. Effects of polymer concentration, shear rates, temperature, and electrolytes on the solution behavior of HAHEC were comprehensively studied, which indicated that the polymers show high viscosification property, excellent viscosity retention in brine water, and surface activity. FTIR, DSC, and UV measurements were applied to characterize the molecular structure and composition of HAFFEC to confirm the incorporation of hydrophobic group into the polymer chain. Atomic force microscope (AFM) and fluorescence spectrum measurements were applied to study the formation of the molecule aggregation and hydrophobic microdomain of HAHEC, and revealed the close relationship between the rheological behaviors and the hydrophobic viscosification effect. (c) 2006 Wiley, Periodicals, Inc.