Synthesis and Self-Assembly Behavior of Chiral Amphiphilic Diblock Copolymers Bearing L-Phenylalanine

Abstract

Novel chiral amphiphilic diblock copolymers bearing L-phenylalanine was synthesized using a “click” reaction of N3-L-phenylalanine and MPEO-b-PGPE. The structure and composition of copolymers were characterized by 1H-NMR and elemental analysis. Additionally, the self-assembly behavior of these chiral copolymers was investigated in sodium dihydrogen phosphate buffer (pH 4.5): the CMC of copolymer MPEO-b-PGTP determined by the measurement of surface tension was 2.1 mg/mL; the size and morphology of the micelles were studied using TEM; the specific optical rotation ([α]25D) of the micellar solutions was also measured; the result indicated that the copolymers can form chiral micelles in sodium dihydrogen phosphate buffer (pH =4.5).In recent years, the synthesis, structure and properties of optically active polymer have been paid attention by scientists owing to its potential applications in chiral separation, asymmetric adsorption, chiral synthesis[1]. The amphiphilic block polymers bearing amino acid possess not only the characteristics of the conventional amphiphilic block copolymer, but also good optically activity and biocompatibility. So it can be employed as nanoreactors for asymmetrical catalysis and materials for drug delivery. But there have been few reports published on the synthesis of chiral amphiphilic copolymers bearing amino acid. Sutthira Sutthasupa reported the synthesis of amino acid-based norbornene block copolymer with ester and carboxyl groups as hydrophobic and hydrophilic units[2]. O’Reilly group synthesized the amino acid-based chiral amphiphilic block copolymers using RAFT technique, and elucidated its self-assembly into spherical micelles with optically active hydrophobic core[3]. In the present work, chiral amphiphilic diblock copolymers bearing L-phenylalanine (L-Phe) pendants poly(ethylene oxide)-b-poly (glycidyl triazolyl-L-phenylalanine) (MPEO-b-PGTP) have been synthesized by the modification of poly(ethylene oxide)-b-poly (propargyl glycidyl ether) (MPEO-b-PGPE) with L-phenylalanine.