Synthesis and Solution Self-assembly of Poly(L-Lactide)-based Amphiphilic Block Copolymers

Nanostructures based on biocompatible and biodegradable polymers are desirable for numerous biomedical applications. An amphiphilic block copolymer, poly(L-lactide)-b-poly(acrylic acid) (PLLA-b-PAA), was synthesized by combination of ring-opening polymerization (ROP) of L-lactide and reversible-addition fragmentation chain transfer (RAFT) polymerization of tert-butyl acrylate, a protected acrylic acid. Methoxy-terminated poly(ethylene glycol)-amine, a protein-repellent polymer, was conjugated to a portion of the PAA block to prepare a brush copolymer, PLLA-b-P(AA-r-PEGAm). The self-assembly of these amphiphilic block copolymers was explored in dilute aqueous solution using a solvent-switch method. A number of morphologies were observed when the self-assembly conditions (e.g., solvent, concentration, temperature) were varied. These structures included fibers, lozenges, and intermediate fiber-lozenge structures. The most intriguing result was that PLLA-b-PAA formed well-defined lozenge-shaped structures when the self-assembly was performed at 55 °C. The -COOH groups on the PAA corona of the micelles were used to coordinate to cisplatin, demonstrating the potential of the micelles to be employed as nanocarriers for drug delivery.M.Sc