In this review we outline the various methods that have been explored to synthesize architecturally defined nanoparticles from discrete polymer chains, summarize the methods of characterization that are required to prove their formation and probe their morphology, and introduce a number of potential applications that are being explored currently. Given the small size of the nanostructures produced by these methods and the relative ease with which they can be tailored to specific end use applications it is likely such efforts will intensify in the coming years. So far, simple chemistry has been utilized and high-level characterization and modeling studies have been applied to understand the process by which these particles form and how they behave, both in the bulk and in solution. Although impossible to predict where this work will lead, we hope this "user's guide" will prove useful to the community as research on singlechain nanoparticles continues to evolve.From left to right:
An efficient route to architecturally defined, sub-20 nm soft nanoparticles fabricated from single polymer chains via intramolecular photodimerization of pendant anthracene units is presented. Photodimerization is confirmed by the disappearance of the characteristic anthracene π-π* absorption peak at ≈ 360 nm measured by UV-vis spectroscopy. Size exclusion chromatography (SEC) with UV, multi-angle light scattering (MALS), and viscometric detection confirms that as photodimers form, the chains fold to form nanoparticles, demonstrated by shifts in the SEC traces to longer retention times as a function of increased irradiation time. These shifts indicate a reduction in hydrodynamic radius, corroborated and quantified by viscometric data. MALS detector traces reveal the presence of a small amount of chain-chain coupling during this process, but confirm that this is primarily a single-chain phenomenon. Electron microscopy provides visual confirmation of nanoparticle formation.
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