Methyl methacrylate triblock copolymer, which can be synthesized by group transfer polymerization, is a multifunctional polymer. Triblock copolymer consists of blocks of monomer with various properties, such as molecular weight, hydrophobicity and charge. It can be utilized for various bioseparation processes. Furthermore, the arrangements of sequences and sizes of the blocks provide rich solution behavior for various purposes. The concepts of molecular engineering and molecular design can be applied to the synthesis of this triblock copolymer and its application. In this research, copolymer B(8)M(12)A(16) was modified using iminodiacetic acid to chelated copper ions for protein affinity coprecipitation, where B represents methyl methacrylate group, M is 2-(dimethylamino) ethyl methacrylate group and A is methacrylic acid group. The chemical structure and the physical properties of the modified copolymer were investigated to ensure that the copolymer was modified accordingly. Finally and most importantly, preliminary coprecipitation experiments that involve three different kinds of proteins - lysozyme, myoglobin and hemoglobin - are preformed. Results show that Hemoglobin can be coprecipitated with B(8)M(12)A(16)-IDA-Cu by affinity interaction but not for Lysozyme or Myoglobin. These results are attributed to the various numbers of exposed histidine residues of protein and the degrees of modification of the chelating agent in the triblock copolymer. In conclusion, the potential for utilizing modified triblock copolymer for selective affinity coprecipitation was revealed.