Visible Light-Driven MADIX Polymerisation via a Reusable, Low-Cost and Non-Toxic Bismuth Oxide Photocatalyst

The continuous amalgamation of photocatalysis into existing reversible deactivation radical polymerisation processes has initiated a rapidly propagating area of polymer research in recent years. We introduce bismuth oxide (Bi2O3) as a heterogeneous photocatalyst for polymerisations, operating at room temperature with visible light. We demonstrate formidable control over degenerative chain-transfer polymerisations, such as macromolecular design by interchange of xanthate (MADIX) and reversible addition-fragmentation chain transfer (RAFT) polymerisation. We achieved narrow molecular weight distributions and attribute the excellent temporal control to a photo-induced electron transfer (PET) process. This methodology was employed to synthesise diblock copolymers combining differently activated monomers. The Bi2O3 catalyst system has the additional benefits of low toxicity, reusability, low-cost, and ease of removal from the reaction mixture.Australian Research Counci

Lichtinduzierte MADIX Polymerisation im sichtbaren Spektrum durch wiederverwendbares, preiswertes und ungiftiges Bismutoxid als Photokatalysator

Der Einbezug von Photokatalyse in Methoden der Reversiblen Deaktivierung Radikalischen Polymerisation (RDRP) hat in den letzten Jahren ein schnell wachsendes Forschungsfeld in der Polymerforschung begründet. In diesem Artikel präsentieren wir die Verwendung von Bismutoxid (Bi2O3) als heterogenen Photokatalysator für Polymerisationen, welcher unter Bestrahlung mit sichtbarem Licht bei Raumtemperatur aktiv ist. Bismutoxid als Katalysator weist hervorragende Kontrolle bei degenerativen Kettentransferpolymerisation auf, u.a. makromolekulares Design durch den Austausch von Xanthaten (MADIX) und Reversibler Additions-Fragmentierungs Kettentransfer (RAFT) Polymerisation. Es wurden eng verteilte Molekulargewichtsverteilungen erzielt, welche, neben einer exzellenten zeitaufgelösten Kontrolle, einem photoinduzierten Elektronentransfer (PET) Prozess zuzuschreiben sind. Diese Methode wurde zur Synthese von Diblockcopolymeren verwendet, bei dem u.a. unterschiedlich stark aktivierte Monomere zum Einsatz kamen. Bismutoxid als Katalysatorsystem zeichnet sich u.a. durch geringe Toxizität, Wiederverwendbarkeit, geringe Kosten als auch simples Entfernen vom Reaktionsgemisch aus

RAFT without an “R-Group”: From Asymmetric Homo-telechelics to Multiblock Step-Growth and Cyclic Block Copolymers

The amalgamation of photoredox catalysis and reversible-deactivation radical polymerization (RDRP) has offered new avenues of controlling polymer synthesis in recent years. Additionally, the incorporation of bismuth oxide catalysts offers advantages to overcome the limitations of current endogenous catalysis. In this study, we used bismuth oxide to employ dithiocarbonyl disulfides as chain transfer agents (CTAs) in reversible addition–fragmentation chain transfer (RAFT) polymerizations. Despite using CTA precursors with a symmetric molecular structure, we show that the corresponding homo-telechelic (co)polymers propagate with asymmetric growth in one direction only. We employed this methodology to produce homo-telechelic AB diblock copolymers and ABC triblock terpolymers, which after aminolysis can undergo reversible oxidative step-growth polymerization or ring-closure to form either unusual multiblock copolymers or cyclic block copolymers

Activating ATRP Initiators to Incorporate End-Group Modularity into Photo-RAFT Polymerization

Heterogeneous photocatalysis is increasingly used in reversible deactivation radical polymerization (RDRP). In this study, we found that alkyl bromide redox chemistry typically found in atom transfer radical polymerization (ATRP) can be incorporated in concert with dithiocarbonyl disulfide chemistry into the reversible addition–fragmentation chain transfer (RAFT) process via bismuth oxide photocatalysis. This amalgamation of mechanisms introduces end-group modularity—a new layer of control—into RAFT polymers uniquely enabled by photoredox catalysis. We found that a diversity of functionality can be installed at the α-end group via alkyl bromides, while the molecular weight distribution can be tuned seamlessly at the ω-end group through the simultaneous addition of multiple disulfides