Synthesis and application of pH-responsive branched copolymer nanoparticles (PRBNs): a comparison with pH-responsive shell cross-linked micelles

pH-responsive polymers are both a fascinating and fundamentally important class of polymer. The ability to change their aqueous solution properties and behavior in response to simple external stimuli-that is, the addition of acid or base-places them uniquely as: (i) 'building blocks' for the fabrication of higher-order materials via self-assembly, (ii) controllable encapsulation and release devices and, (iii) useful synthetic mimics of highly complex natural biological systems. The fabrication of pH-responsive branched copolymer nanoparticles (PRBNs) which are capable of reversibly forming distinct 'core-shell' morphologies is an emerging class of material. In this highlight, we discuss key advances in the synthesis, characterization and application of branched pH-responsive copolymer nanoparticles and place these developments in the context of seemingly similar structures-most notably shell cross-linked micelles. We also speculate as to the scope, and limitations, of these branched materials in various commercial and fundamental applications.