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A straightforward method is described to achieve polymeric nanoparticles by double folding of single linear chains. The side chain functional polystyrene with controlled molecular weight is converted to pendant azide and benzophenone motifs via postmodification reactions. Resulting functionalized chains undergo intramolecular crosslinking upon ultraviolet (UV) illumination using simultaneous and subsequent pathways at a dilute concentration. Particle size of nanoparticles can be tuned by changing the degree of crosslinking using a second folding process. Obtained single and double collapsed chains indicate higher glass transition temperatures and lower hydrodynamic radii compared to their intermediates. To our knowledge, the combination of photoinduced azide crosslinking and radical coupling processes is the first attempt to prepare double folding single polymer chains.

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Light-responsive crosslinked structures were prepared by a straightforward quaternization strategy using chloride functional polystyrene copolymers and commercially available Michler's ketone with varying feed ratios. Resulting organogels demonstrated excellent solvent absorption and their swelling characteristics were altered by UV-light irradiation. According to scanning electron microscope images, UVilluminated samples showed an obvious photodecomposition, which enhanced their solvent uptake capacity with increase of UV exposure. Additionally, release behavior of eosin Y as a model compound was determined by UV-vis and fluorescence spectrometers. Achieved photoactive gels were also employed as the reusable heterogeneous initiators for photoinduced free-radical polymerization of methyl methacrylate.

Front Cover: In article number 1900116, Gokhan Temel and co‐workers discuss a straightforward method to achieve polymeric nanoparticles by double folding of single linear chains via photoinduced radical coupling and azide crosslinking using simultaneous and subsequent pathways. Particle size and glass transition temperature of resulting nanoparticles can be altered by the second folding/collapse process.