A series of methacrylic triblock copolymers were synthesized. The potential of using these copolymers as displacers or spacers in hydrophobic interaction chromatography (HIC) was discussed. It was found that selected copolymers were able to separate pancreatic trypsin and alpha-chymotrypsin in an Octyl-Sepharose HIC column. The hydrolytic activities of these two enzymes were not affected by the presence of copolymers. The advantages of methacrylic triblock copolymers were their relatively low molecular mass and the reversible precipitability. These properties make the separation between copolymers and proteins easier. The hydrophobicity of the triblock copolymers could be roughly adjusted by controlling the length of each block. But accurate prediction of their hydrophobicity according to the corresponding chemical structure requires further studies. (C) 1998 Elsevier Science BV. All rights reserved.