Controlling Morphological Transitions of Polymeric Nanoparticles via Doubly Responsive Block Copolymers

Abstract

We report on a dual-responsive block copolymer system that exhibits a pH-dependent cloud point (Tcp) and allows for precise control over the size and morphology of self-assembled nanostructures. By incorporating 2-(dimethylamino)ethyl methacrylate (DMAEMA), a pH- and temperature-responsive monomer, within the corona of a nanoparticle, the relative hydrophilic/hydrophobic block volumes can be controlled. Capitalizing on this phenomenon, we explore the temperature response of block copolymer assemblies at acidic, neutral, and basic pH, where the DMAEMA units are 99, 60, and 2% protonated. In general, as pH decreases, the corona was observed to swell due to charge repulsion and increased hydration, attenuating temperature sensitivity. By systematically varying the pH, temperature, and content of DMAEMA, we develop several systems that can readily form micelles, worms, and vesicles from a single block copolymer composition.