Recently, polymerization-induced self-assembly (PISA) has become widely recognized as a robust and efficient route to produce block copolymer nanoparticles of controlled size, morphology, and surface chemistry. Several reviews of this field have been published since 2012, but a substantial number of new papers have been published in the last three years. In this Perspective, we provide a critical appraisal of the various advantages offered by this approach, while also pointing out some of its current drawbacks. Promising future research directions as well as remaining technical challenges and unresolved problems are briefly highlighted.

Polymerization-induced self-assembly (PISA) is used for the highly convenient and efficient preparation of ampholytic diblock copolymer nanoparticles directly in acidic aqueous solution. Cationic nanoparticles comprising a protonated polyamine stabilizer block and a hydrophobic polyacid core-forming block are formed at pH 2. Micelle inversion occurs at pH 10 to produce anionic nanoparticles with an ionized polyacid stabilizer block and a hydrophobic polyamine core-forming block. Macroscopic precipitation occurs at around pH 6–7, which lies close to the isoelectric point of this ampholytic diblock copolymer. Incorporation of fluorescein and rhodamine dye labels into the acid and amine blocks, respectively, leads to dual-color bifluorescent self-reporting pH-responsive nanoparticles.

Poly(phenyl acrylate) has a sufficiently high glass transition temperature to enable TEM studies of the morphology of diblock copolymer nano-objects prepared using three different polymerization-induced self-assembly (PISA) formulations.

A series of ionic diblock copolymer nanoparticles was prepared in a typical nonpolar solvent (n-dodecane) via polymerization-induced self-assembly (PISA). A single cationic repeat unit was incorporated into the poly(stearyl methacrylate) (PSMA) stabilizer of otherwise uncharged poly(stearyl methacrylate)-poly(benzyl methacrylate) (PSMA-PBzMA) diblock copolymers nanoparticles. By using short PSMA stabilizer blocks, it was possible to obtain nanoparticles with the range of morphologies expected (spheres, worms, and vesicles). For nanoparticles where all stabilizer chains possessed an ionic group, higher-order morphologies were obtained at lower BzMA degrees of polymerization than corresponding uncharged particles, and the particles were electrophoretic. For nanoparticles where only a fraction of the stabilizer chains contained an ionic group, higher-order morphologies were obtained at precisely the same PBzMA degrees of polymerization, and the electrophoretic response was greater than when the shell was fully ionic. These particles with a partially ionic shell are a fascinating system, providing morphologies that can be predicted from existing knowledge of the diblock copolymer morphology yet with the highest possible electrophoretic mobility.

The addition of Hydrogen Iodide to organometal halide perovskite precursor solution at 1% by volume leads to a 10 significant enhancement in average power conversion efficiency (PCE) in inverted solar cell devices, increasing from 7.7% 11 to 11.9% and 6.1% to 10.0% in spin-cast and spray-cast devices respectively. We directly attribute this improved device 12 performance to increased thin-film surface coverage coupled with higher optical density. X-ray diffraction studies also 13 reveal that the HI additive facilitates full conversion of the precursor material to the crystalline perovskite phase. From 14 solution studies, we relate these changes in device performance to the presence and distribution of precursor aggregates 15 that effectively pattern the formation of perovskite crystals during film formation. 16