Preparation of Single Chain Nanoparticles via Photoinduced Double Collapse Process

Abstract

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.

Advances in Phototriggered Synthesis of Single-Chain Polymer Nanoparticles

“…Interestingly, these authors performed a clear comparison between SCNPs prepared through simultaneous against sequential, photoactivated double folding (see next section). Figure 16-right shows SCNP fabrication using the sequential, photoactivated double folding of a precursor containing azide and benzophenone moieties, as recently reported by Temel and coworkers [55]. Intrachain nitrene C-H insertion upon azide decomposition was selected as the first folding process.…”

Macromolecular Superstructures: A Future Beyond Single Chain Nanoparticles

“…To initiate the intrachain crosslinking of single polymer chains, a wide variety of chemical reactions has been developed over the last decade, which were discussed in significant detail in reviews and books . The extensive toolbox of reactions allows for versatile synthetic access, a high tolerance of functional groups and even orthogonal folding conditions for multi‐step folding reactions . Large scale synthesis of SCNPs, which is paramount for future applications, remains elusive despite the great variety of folding chemistries.…”

“…As the desired intrachain reaction competes with the parasitic interchain reaction, concentrations <1 mg mL −1 are the current standard to achieve a selectivity for the intramolecular folding . Some examples require even lower concentrations of 0.02 mg mL −1 , 0.03 mg mL −1[17] or 0.04 mg mL −1 . Such low concentrations do not only drastically limit the scalability of SCNP synthesis, yet critically impede the online monitoring of the reactions – paramount towards improving our understanding of the folding process.…”

“…multi-step folding reactions. [11][12][13][14] Large scale synthesis of SCNPs, which is paramount for future applications, remains elusive despite the great variety of folding chemistries. The largest hurdle in the scale-up of SCNP synthesis is currently the highly dilute concentrations of the intramolecular crosslinking, which prevent the development of strategies to produce SCNPs beyond the gram scale.…”

Single‐chain polymer nanoparticles via click crosslinking and effect of photoinduced radical combination on crosslink points

“…In our previous work, we introduced single-chain nanoparticles via photoinduced radical coupling (PRC) strategies. 22,23 Pendent benzophenone containing copolymers were transformed into polymeric nanoparticles by single or double folding processes under UV light illumination at high dilution conditions. According to corresponding studies, the combination of ketyl radicals resulting from photolysis of the pendent benzophenone species was employed to build collapsed nanoparticles.…”