Mechanistic Insights into the Alternating Copolymerization of Epoxides and Cyclic Anhydrides Using a (Salph)AlCl and Iminium Salt Catalytic System

Abstract

Mechanistic studies involving synergistic experiment and theory were performed on the perfectly alternating copolymerization of 1-butene oxide and carbic anhydride using a (salph)AlCl/[PPN]Cl catalytic pair. These studies showed a first-order dependence of the polymerization rate on the epoxide, a zero-order dependence on the cyclic anhydride, and a first-order dependence on the catalyst only if the two members of the catalytic pair are treated as a single unit. Studies of model complexes showed that a mixed alkoxide/carboxylate aluminum intermediate preferentially opens cyclic anhydride over epoxide. In addition, ring-opening of epoxide by an intermediate comprising multiple carboxylates was found to be rate-determining. On the basis of the experimental results and analysis by DFT calculations, a mechanism involving two catalytic cycles is proposed wherein the alternating copolymerization proceeds via intermediates that have carboxylate ligation in common, and a secondary cycle involving a bis-alkoxide species is avoided, thus explaining the lack of side reactions until the polymerization is complete.

Switchable Polymerization Triggered by Fast and Quantitative Insertion of Carbon Monoxide into Cobalt–Oxygen Bonds

“…Forschungsartikel CO;3)visible light initiated OMRP of acrylates.The ampules were kept in the dark (wrapped by aluminum foil) during steps 1a nd 2. Ther eactions were monitored by 1 HNMR analysis of aliquots taken at regular intervals.Atfirst, PO,P A and MA were used as the model substrates ( Table 1, entries [1][2][3][4][5]. Given that CO and visible light could provide temporal control over the ROCOP/OMRP switch and the OMRP process,r espectively,i ti sp ossible to precisely manipulate the incorporation of monomers into the resulting polymer chains.T aking entry 1f or example,R OCOP and OMRP occurred during the first stage and the third stage, respectively,a sr evealed by the 1 HNMR spectra (Fig-Figure 2.…”

“…Ther ing-opening copolymerization (ROCOP) of epoxides/anhydrides has emerged as ab urgeoning method to produce polyesters. [5] Thew ide availability of renewable monomers and the opportunity for post-polymerization modification open access to am yriad of new materials with unique properties that are not accessible through traditional condensation reactions. [6] Cobalt Salcy [bis(salicylaldimine)] complexes featuring nucleophilic axial groups [(Salcy)Co III X; X = halides,c arboxyl, etc.…”

Phthalic anhydride promoted ring‐opening polymerization of cyclohexene oxide catalyzed by dinuclear chromium complex supported by piperazine‐bridged [ONSO] ligand

“…Based on the experimental phenomena discussed above and references, the ROP of CHO catalyzed by piperazine‐bridged [ONSO]CrCl dinuclear complex in the presence of PA is speculated to undergo a cationic pathway. The first stage is that PA interacts with the dinuclear chromium complex, leading to the generation of carbocation active species.…”

Schaltbare Katalyse zur Herstellung von Multiblock‐Polyestern aus einer Mischung von Propylenoxid, Lactid und Phthalsäureanhydrid

“…LA ROP läuft dabei über ein Alkoxid‐Intermediat ab ( k 3 ). Es ist zu beachten, dass der detaillierte Mechanismus von Al‐Salen‐Katalysatoren für Anhydrid/Epoxid‐ROCOP vor kurzem von Coates, Tolman und Mitarbeitern untersucht wurde . Sie beobachteten deutliche Farbwechsel während der Reaktion und schrieben die tiefrote Farbe am Ende der Reaktion der Bildung einer Al‐Bisalkoxid‐Spezies zu, welche am Ende von ROCOP auftrat.…”