Size and morphology control of aggregates from supramolecular graft copolymers stabilized by ionic interaction

Abstract

A series of supramolecular graft copolymers (SGPs) composed of poly($_L-lysine$) (PLL) as a main chain and poly($_{D,L}-lactic-co-glycolic acid$) (PLGA) as a side chain was synthesized with different degrees of substitution (DSs) through ionic interaction in a DMSO solvent. The addition of water induced the self-assembly of PLL-PLGA SPGs into spherical micelles at a critical water content (CWC). The size of the spherical micelles at each CWC decreased with an increase of DS and core-shell structures, which was confirmed by XPS and zeta-potential measurements. The morphological transitions were driven under thermodynamic control when the solvents mixed. Consequently, further increases of water content caused the transition of the spherical mi-celles to vesicles, while the initial spherical micelles were reconstructed from vesicles when the DMSO was added. The content of water, the boundaries for the morphology transition, depended on the DS. The pH and salt levels affected the stability of the aggregates weakening the ionic interactions between the PLL and PLGA.