Maleimide-poly(ethylene glycol)-b-poly(ε-caprolactone) is a functionalized, amphiphilic, diblock copolymer composed of a hydrophilic PEG block and a hydrophobic PCL block. These biodegradable, biocompatible polymers can self-assemble to form nanoparticles, such as micelles and polymersomes, in both aqueous and non-aqueous media. Due to these properties, these polymers are widely used in polymeric nanoparticle formulation to achieve controlled and targeted delivery of therapeutic agents (e.g. APIs, genetic material, peptides, vaccines, and antibiotics). Additionally, well-defined nanoparticles with tunable size and properties can be prepared by altering the molecular weight ratios between hydrophilic and hydrophobic blocks, as well as by controlling formulation parameters. The carboxylic acid functional group on the PEG chain enables rapid and facile surface functionalization, allowing for these materials to be used in applications such as targeted drug delivery.