Synthesis of an Amphiphilic Star Triblock Copolymer of Polystyrene, Poly(ethylene oxide), and Polyisoprene Using Lysine as Core Molecule

A new amphiphilic ABC star triblock copolymer, with polystyrene (PS) and polyisoprene (PI) as hydrophobic segments and poly(ethylene oxide) (PEO) as hydrophilic segment, is successfully prepared using lysine as a core molecule. The mPEO with blocked methoxyl group at one end and hydroxyl at another end, PS, and PI with hydroxyl end groups are obtained by the anionic technique. The hydroxyl groups of mPEO-OH and PS-OH are converted into succinimidyl carbonate first and then coupled with ε and α amino groups of lysine, respectively, to yield an intermediate mPEO-PS-Lys-COOH. The PI-OH is also converted into PI carbonate (PI-SC) and then PI-NH 2 and reacted with a carboxyl group of lysine at the junction of PS and mPEO arms of mPEO-PS-Lys-COOH in the presence of N,N ‘-dicyclohexylcarbodiimide (DCC). The molecular weight distribution of the final product mPEO-PS-PI is rather narrow (<1.15). The structure of intermediates and final products was characterized by NMR, IR, UV, and SEC in detail. This method is promising for the synthesis of star copolymers with multiarms of different chain structure.