Redox Active Compounds in Controlled Radical Polymerization and Dye-Sensitized Solar Cells: Mutual Solutions to Disparate Problems

Polymer Colloids: Current Challenges, Emerging Applications, and New Developments

Polymer colloids are complex materials that have the potential to be used in a vast array of applications. One of the main reasons for their continued growth in commercial use is the water-based emulsion polymerization process through which they are generally synthesized. This technique is not only highly efficient from an industrial point of view but also extremely versatile and permits the large-scale production of colloidal particles with controllable properties. In this perspective, we seek to highlight the central challenges in the synthesis and use of polymer colloids, with respect to both existing and emerging applications. We first address the challenges in the current production and application of polymer colloids, with a particular focus on the transition toward sustainable feedstocks and reduced environmental impact in their primary commercial applications. Later, we highlight the features that allow novel polymer colloids to be designed and applied in emerging application areas. Finally, we present recent approaches that have used the unique colloidal nature in unconventional processing techniques.

Enhanced synthesis of oxo-verdazyl radicals bearing sterically-and electronically-diverse C3-substituents

The synthetic viability of the hydrazine- and phosgene-free synthesis of 1,5-dimethyl oxo-verdazyl radicals has been improved via a detailed study investigating the influence of the aryl substituent on tetrazinanone ring formation. Although it is well established that functionalisation at the C3 position of the tetrazinanone ring does not influence the nature of the radical, it is crucial in applications development. The synthetic route involves a 4-step sequence: Schiff base condensation of a carbohydrazide with an arylaldehyde, alkylation, ring closure then subsequent oxidation to the radical. We found that the presence of strong electron-donating substituents and electron rich heterocycles, result in a significant reduction in yield during both the alkylation and ring closure steps. This can, in part, be alleviated by milder alkylation conditions and further substitution of the aryl group. In comparison, more facile formation of the tetrazine ring was observed with examples containing electron-withdrawing groups and with meta- or para-substitution. Density functional theory suggests that the ring closure proceeds via the formation of an ion pair. Electron paramagnetic resonance spectroscopy provides insight into the precise electronic structure of the radical with small variations in hyperfine coupling constants revealing subtle differences.