The invention provides composite porous membranes comprising a porous hydrophobic substrate coated with difunctional surface-modifying molecules. The difunctional surface-modifying molecules provide a hydrophilic surface without forming branches of interconnected polymer molecules in the pores. The invention also provides a method for making composite porous membranes, such as a composite hydrophilic membrane with reduced concentration of surface modifying molecules required to coat a hydrophobic substrate.